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Police in Guinea-Bissau have detained five prominent opposition politicians - including a former prime minister. 

The arrests come as the country prepares for early elections on 20 April. 

All five of those detained are members of the African Party for the Independence of Guinea-Bissau and Cape Verde, or PAIGC, which is the third-largest party. 

Arrests seem to have no end Carlos Gomes Junior, leader of PAIGC

Among them are the former prime minister Carlos Correia and the former economy minister Filinto Barros. 

The party's president Carlos Gomes Junior said the incident had caused "deep unease over the current situation in Guinea-Bissau, where the arrests seem to have no end". 

Other members of the opposition have been imprisoned in recent weeks, although most have now been released. 

The vice-president of Guinea-Bissau's Human Rights League Joao Vaz Mane has been detained for over two weeks without being charged. 

'Prisoner of conscience'

Amnesty International says it will campaign on his behalf. 

Last week the government closed down the independent Radio Bombolom which is run by a member of the opposition. 

The government said the station could "potentially cause irreparable damage, even to the country's independence". 

Elections were scheduled for the end of 2003. 

But in November President Kumba Yala sacked his government and the following month said elections would be held earlier. 

He has been accused of trying to establish a dictatorship in the former Portuguese colony. 

Colombian President Alvaro Uribe has defied rebel threats and gone ahead with a visit to the south-western town of Neiva a day after 17 people died in an explosion there. 

The blast destroyed a house under the flight-path to the airport as it was being searched by police who had received a tip-off linking it to a plot to bring down the president's plane. 

It's a provocation for the guerrillas, and we're the ones who will pay Alfredo Vargas, Neiva resident speaking of the president's visit

The BBC's correspondent in Colombia, Jeremy McDermott, says it now appears the tip-off came from Marxist guerrillas who planted explosives in the house which were detonated when the police broke in. 

Meanwhile troops are combing the jungles of southern Colombia searching for three Americans who were kidnapped, reportedly by rebels from the Revolutionary Armed Forces of Colombia (FARC), after their plane crash landed on Thursday. 

Rebels not intimidated

In Neiva Mr Uribe met the families of those killed in the bomb at a funeral home and visited the 30 injured survivors at a local hospital. 

Mr Uribe's tough stance against the rebels is not working

The authorities have blamed the explosion on FARC guerrillas who have stepped up their campaign of violence in response to the president's get-tough policy towards the rebels. 

Mr Uribe, who has already survived more than half a dozen assassination attempts in his political career has vowed to crush the rebels. 

Our correspondent says the president is talking and acting tough, but the guerrillas are not intimidated and, instead, are themselves acting tougher than ever, no matter what the cost in civilian lives. 

Last week 35 people were killed by a bomb in the capital, Bogota. 

Search for hostages

Some of the people near the scene of the bomb blast in Neiva fear the president's presence could make matters worse. 

"It's a provocation for the guerrillas, and we're the ones who will pay," said Alfredo Vargas, a teacher whose home was damaged in the explosion. 

The search for the US hostages is underway

Mr Uribe has the backing of the United States. Three of its citizens, believed to be contractors working for the CIA, are now in guerrilla hands after their plane came down in the south of the country. 

The four Americans and one Colombian on board were all reportedly alive when their single-engine Cessna crashed in the jungles of Caqueta province. 

FARC rebels reached the survivors before local army units could find the plane, and killed one American and the Colombian "execution-style, in cold blood", according to General Jorge Enrique Mora, Colombia's senior military commander. 

A massive search is now underway to locate the remaining three hostages. 

General Mora said that helicopters, reconnaissance planes and special forces troops were all being used in the search. 

"We have nothing new, and (the US nationals) have not been found. An intensive operation is under way. The objective is to find the three men," he added. 

North Koreans have been competing to show their devotion to their autocratic leader, Kim Jong-il, as a public holiday is held to mark his 61st birthday. 

But the lavish celebrations were accompanied by a call to the military to be on high alert - the communist state is locked in a deepening stand-off with the United States. 

All party members and workers must burn with hatred and hostility in their hearts toward US imperialists Rodong Sinmun newspaper

Parades, flower shows (featuring the flower named after him), concerts and firework displays have been held around the country. 

The celebrations were held despite a serious economic crisis, in which many people are reported to have starved to death. 

Pyongyang has engaged in an escalating war of words with Washington since October, when reports emerged that it had restarted its nuclear programme. 

Kimjongilia

Kim Jong-il's birthday is a national holiday in North Korea, and people have long been preparing for the country's most important event. 

Kim is reportedly grooming his successor

On Tuesday, about 50,000 gathered in Pyongyang to pledge their allegiance to Mr Kim, known as the Dear Leader. 

During the main festivities which started at the weekend, generals read poems hailing the leader and the army organised huge fireworks displays. 

Newsreaders on state television provided running commentaries for the event. 

As part of the celebrations, an exhibition of 30,000 flowers - all of one variety - has opened in Pyongyang. 

The Kimjongilia flowers are named after Mr Kim, and a number of government departments and army units have been reportedly competing to make the best bouquet arrangements. 

Government officials also have been visiting a log-cabin on Paektu Mountain - a purported birthplace of Mr Kim, although western historians say Kim Jong-il was born in Russia's far east. 

Mr Kim came to power in 1994 after the death of his father, Kim Il-sung, and a huge cult of personality has been built up around them. 

Until three years ago he remained one of the world's most reclusive leaders - rarely seen, let alone heard in public. 

That changed when he held a historic summit with South Korean President Kim Dae-jung, and hosted a visit by former US Secretary of State Madeleine Albright. 

Earlier this year, Japanese media reported that Mr Kim's second son, 21-year-old Kim Jong Chul, is being groomed as his successor, ready to continue the communist dynasty. 

Festivities overshadowed

This year's celebrations come amid a growing crisis over North Korea's nuclear programme. 

The youths pledged their allegiance to the Great Leader

Last week, the International Atomic Energy Agency (IAEA) referred North Korea to the United Nations Security Council for breaking its nuclear agreements. 

The state-run newspaper Rodong Sinmun, monitored by the South Korean Yonhap news agency, accused the US of pushing the dispute with Pyongyang "to the brink of war". 

"All servicemen of the Korea People's Army should always be on the alert," the newspaper's editorial said. 

"All party members and workers must burn with hatred and hostility in their hearts toward US imperialists." 

A state in southern Brazil has ignited a storm by taking back control of the state water utility from French group Vivendi. 

The decision to remove the holding company in which Vivendi has a stake from the running of Sanepar, as the utility is known, comes after complaints about both water quality and under-investment. 

A source close to Sanepar told Reuters that the decision to wield its 60% majority stake in the company sent worrying signals for foreign investors - just as new President Lula da Silva is trying to woo them back after a rocky 2002 for the Brazilian economy. 

No-one puts money into a Brazilian company without getting some control," the source said. "Changing the rules of the game now that everyone has invested makes no sense." 

'Social service'

Although Domino Holding, a group comprising Vivendi, asset management firm Opportunity and Brazilian builder Andrade Gutierrez SA, holds just 40% of Sanepar, a deal with the previous governor gave them power over staffing, loans, deals with shareholders and final say over tariffs. 

But the current incumbent running the state - home to the massive Iguacu waterfalls - says his predecessor never signed the relevant decree. 

"(The state government) understands that sanitation is not an activity to make a profit but a social service," a spokesman for Sanepar said. 

The company has monopoly control over water and sewage for the state's 7.5 million people. 

Dirty water?

The news comes amid a chorus of disapproval of water privatisations, notably several in Latin America which have allegedly gone badly wrong. 

The Centre for Public Integrity, a US-based research group, is in the process of publishing a 10-part series by the International Consortium of Investigative Journalists outlining a series of problems with privatisations from Argentina to Australia. 

"The Water Barons" expose accuses Vivendi, among other companies, of taking over water utilities worldwide by taking advantage of the doctrines of international groups such as the World Bank, which demand privatisation as the quid pro quo for development aid. 

Its water-based profits have risen from $5bn in 1990 to over $12bn by 2002, the CPI says. 

Among Vivendi's operations in 43 countries is one in Argentina, where - the CPI alleges - the 30-year concession to run Aguas Argentinas has produced a catalogue of unfulfilled improvements coupled with International Monetary Fund-backed increases in government payouts to the company. 

South Africa's President Thabo Mbeki has said he wants to jumpstart black participation in the white-dominated economy. 

At the opening of parliament on Friday Mr Mbeki said the government would soon introduce rules to give the black majority a bigger role in the economy. 

But he also added that "a rigid and inflexible approach" would not be wise. 

The government will lay greatest stress on black economic empowerment that is associated with growth, development and enterprise development and not merely redistribution of existing wealth Thabo Mbeki South African president

The South African government failed to push through legislation on black economic empowerment last year. 

Mr Mbeki also said he expected gross domestic product to grow by 3.1%, up from original estimates of 2.6%. 

Nine years after the end of the apartheid regime, the South African economy is still plagued by mass unemployment, which some experts say is as high as 30%, and widespread poverty. 

Mining charter

Investors were alarmed and mining stocks plummeted after an initial draft of a black ownership plan for the mining sector was leaked in the middle of last year. 

But the government responded rapidly, ruling out nationalisation and later struck a deal with the industry, labour and government. 

The government approved a mining charter last October which set out a target of 15% black ownership in local mines within five years and 26% within 10 years. 

"As we approach the end of the first decade of our new democracy, the need for an economic transformation that brings about effective and significant black economic empowerment, becomes more pressing," Mr Mbeki said in his State of the Nation address in Cape Town. 

He added: "The government will lay greatest stress on black economic empowerment that is associated with growth, development and enterprise development and not merely redistribution of existing wealth." 

The South African president said he wanted to call a special summit of business, labour, government and community leaders in May to discuss ways to boost growth. 

The Chamber of Mines, which represents the country's biggest mining companies, said the speech was "positive and encouraging". 

Economists and industry also welcomed the address, although financial markets moved very little. 

 

By Steve Schifferes  BBC News Online in Washington

After months of wrangling, the US Congress has finally agreed how much money the US government will be able to spend on its key domestic programmes. 

There is more pork with one vote than they have ever passed in their lives Tom Schatz, Citizens Against Government Waste.

The spending bill, which covers all discretionary spending except defence, will come to $397.4bn (£246.7bn), $13bn more than the Bush administration wanted. 

The long and difficult budget process gave plenty of scope for individual Congressmen to add wasteful - or "pork-barrel" - projects that would help their own districts, threatening to hold up the passage of the entire bill. 

Despite the extra cost, President Bush has pledged to sign the budget bill. 

He now faces an even more prolonged battle over the next year's request for funds because to the budget deficit is expected to swell to $300bn. 

Cowgirl Home of Fame 

Fears that Congress would not be able to keep spending in bounds were behind the remarks of Federal Reserve chairman Alan Greenspan earlier in the week that he could not wholeheartedly endorse Mr Bush's budget and tax plans. 

Mr Bush is facing a big budget deficit

And the spending bill provides plenty of examples, including $90,000 for a Cowgirl Home of Fame, $1.5m to repair an historic hotel in Glacier National Park, and $5m for an information campaign featuring McGruff the crime dog. 

There were especially big projects for Alaska and South Carolina, the home states of the key Republican and Democratic Senators on the Appropriations Committee. 

"All the money in this bill is the result of a backroom deal," said Representative David Obey, one of the Democratic negotiators. 

Congress had previously been bound by a budget law which said that any new spending would have to be balanced by a cut in spending somewhere else, but that provision partly expired in November and has not been renewed. 

Negotiators did defeat a proposal for an extra $2.5bn in farm aid, fearing it would anger developing countries that are the middle of crucial trade talks with the United States. 

Critics call the wasteful projects pork. 

"There is more pork with one vote than they have ever passed in their lives," said Tom Schatz of Citizens Against Government Waste. 

Terrorism fears

Despite the increase of $10bn in spending on terrorist-related activities, Democrats said that the states and cities were not receiving enough funds to prepare properly for emergencies. 

They had proposed an additional $2.5bn to help states and cities prepare for a possible attack. 

"There are many egregious items in this bill, especially the lack of funding for critical homeland security needs," said House Democratic Minority Leader Nancy Pelosi. 

Many of the Democrats who are running for President also plan to make the matter of protecting the civilian population one the key issues of their campaign. 

The spending bill also severely restricts a controversial Pentagon programme to counter terrorism by mining the internet for information about individuals. 

The Total Information Awareness Programme, headed by Admiral John Poindexter was intended to spot terrorist activities by monitoring e-mails and commercial databases for suspicious activities. 

Paying for the elderly

It was much criticised by civilian libertarians, and now Congress has banned the US military from spying on US citizens or accessing their records. 

The tortured US budget process is likely to become even more difficult next year. 

The Bush administration has proposed big new spending initiatives for the military and wants to reform Medicare, while asking for a $692bn tax cut on dividend payments. 

Meanwhile, other domestic programmes will be squeezed, with those aimed at poor people especially vulnerable. 

And, in the long run, the looming problem of funding the social security system, which provides state pensions for the elderly, will create its own budget difficulties. 

But the highly partisan nature of this Congress, with its narrow Republican majority, will make it extremely difficult to pass the next budget in time. 

Opposition candidate Tassos Papadopoulos has won the presidential election in Cyprus, defeating veteran incumbent Glafcos Clerides. 

The vote comes at a crucial time for the future of the island, which has been divided into Greek Cypriot and Turkish sectors for nearly 30 years. 

Official results showed Mr Papadopoulos won a surprising 51.5% of the votes, well ahead of Mr Clerides, who took 38.8%. 

The 83-year old president acknowledged defeat in a telephone call to Mr Papadopoulos, wishing him luck. 

In a victory statement, Mr Papadopoulos, a 69-year-old lawyer, said "people have voted for change, given me a mandate". 

"I want to give assurances that this will be a unity government," Reuters news agency quoted him as saying. 

Although Mr Papadopoulos had been ahead in opinion polls, it had been widely expected that he would fail to get the necessary 50% plus one vote in the first round. 

Mr Papadopoulos will take over negotiations on reunifying Cyprus, with less than two weeks to thrash out a deal before a deadline to accept or reject a UN plan. 

However, the BBC's Tabitha Morgan in Nicosia says it is not clear how far Mr Papadopoulos's negotiating position will differ from that of his predecessor. 

Lack of faith

When the UN proposals to reunite the island were first made public last November, Mr Papadopoulos argued they should be rejected without a second glance. 

But since then, he has been keen to stress that he accepts the UN plan as the basis of a future settlement, although he claims he can negotiate better terms for Greek Cypriots. 

President Clerides was trailing in opinion polls

Mr Papadopoulos - who will become the fifth Greek Cypriot president - benefited from the support of the influential communist party, Akel, one of the largest in Cyprus. 

He also picked up votes from Greek Cypriots who believe that Mr Clerides has given away too much in UN-sponsored talks with the Turkish Cypriot leader, Rauf Denktash. 

A recent poll found that 64% of Greek Cypriots doubted that their political leaders could find a political solution in the near future to the island's troubles. 

In January thrice-weekly talks began between Mr Denktash and Mr Clerides aimed at resolving their differences over the current UN plan. 

Mr Denktash has threatened to stand down as leader rather than sign the plan in its present form. 

Enmity

UN Secretary General Kofi Annan is to visit the island next week in an attempt to speed up the diplomatic process. 

Cyprus has been partitioned along ethnic lines since Turkey invaded in 1974 in response to an abortive Greek Cypriot coup aimed at uniting the island with Greece. 

This has been the source of political enmity between the two countries ever since, with Ankara maintaining 40,000 troops on the island. 

Turkey is the only country to recognise Turkish-held northern Cyprus as a separate state. 

Standing up to the United States over Iraq has made France's Dominique de Villepin something of a celebrity foreign minister. 

The UN Security Council gave him uncustomary applause last week when he pleaded for weapons inspectors to be given more time. 

In what was widely regarded as an electrifying performance, he told members "war is always the sanction of failure". 

For many abroad, the French funeral has already been held Dominique de Villepin

Rebuffing an earlier remark by US Defence Secretary Donald Rumsfeld that France and Germany are "old Europe" he said his message came "from an old country... that has known war, occupation, barbarity". 

The US press has vilified the man who, French Prime Minister Jean-Pierre Raffarin proudly told parliament, put France "back on the international scene". 

One newspaper described him as "oily" while another editorialist said the 49-year-old "lacks seriousness" and is "diplomacy-lite". 

'Diplomatic pin-up'

But elsewhere Mr Villepin - who has also been a driving force in efforts to bring peace to Ivory Coast - has been heralded as a hero. 

Describing him as "dashing" and "eloquent" a British newspaper said "if there is such a thing as a diplomatic pin-up, then it is Dominique de Villepin". 

Mr Villepin has held his current post for 10 months, taking office after the right-wing general election victory in June. 

Some said he coveted the prime ministerial chair. 

Chirac: A Villepin admirer

Previously he was Secretary General of the Presidency; he took up the position in 1995 when President Jacques Chirac was first elected. 

But while he is a top adviser to and close friend of the French premier, he is widely held responsible for Mr Chirac's 1997 dissolution of parliament which brought a Socialist-led government to power and began five years of "cohabitation" with the left. 

More recently he has been criticised for hastily brokering the Ivory Coast's peace deal which now hangs in the balance. 

Mr Chirac however allegedly said "Villepin catches on with fantastic speed. It is rare to meet a man like him." 

Among members of parliament his arrogance has reportedly made him unpopular. 

Career diplomat

A career diplomat, Mr Villepin graduated from the prestigious Ecole Nationale d'Administration and has served in Delhi and twice in Washington. 

BIOGRAPHY

Born 14 November 1953 Degree: Arts and Law Ecole nationale d'administration graduate 1980-84 Foreign Ministry - African and Malagasy Affairs 1984-89 French embassy in Washington 1989-92 French embassy in Delhi 1992-3 Foreign Ministry - African and Malagasy Affairs 1993-95 Chief of staff of the Minister of Foreign affairs 1995-02 Secretary-General of the Presidency  7 May appointed French foreign minister

The son of a French politician, he is also a self-published poet and author of several books about contemporary French culture and a biography of Napoleon. 

In "The Cry of the Gargoyle" he warned France that it must not yield to "the temptation of resignation that threatens a nation as torpor overcomes it... For many abroad, the French funeral has already been held". 

In a recent interview with the Washington Post he said "the absence of power is the problem in world affairs. Look at the Middle East. Or take Russia. We need a strong Russia on the world scene". 

He said diplomacy and poetry could be combined because they "both rely on the alchemy of paradox". 

"We mix fear and hope, power and weakness, love and hate to find a way out of the impossible... Americans should understand that. They live in a country that has a dream, shaped by the Mayflower and Ellis Island." 

Paris pact Air rage Romanian remains Swede success Festival devotion Together with Berezovsky

Cancer cells can be destroyed using a colourful combination of chemical ingredients, researchers have discovered. 

Using red light, blue dye and a plant hormone, scientists have been able to kill around 99% of cells in laboratory tests. 

As all three ingredients have been used in other therapies before, scientists from Cancer Research UK are hopeful it could be used as a cancer treatment in the near future. 

Researchers from the Gray Cancer Institute in Middlesex, say the treatment is better than conventional photodynamic therapy which destroys tumours with beams of light, because that relies on a good supply of oxygen, which is not available from cancer cells, to work. 

It is a further step in the direction of producing a therapy that directly targets the tumour Sir Paul Nurse Cancer Research UK

The new method uses molecules of indoleacetic acid (IAA), a plant hormone as "fuel" instead. 

This means it can get right to the heart of tumours, where oxygen levels are often very low. 

'Major challenge'

Scientists treated the cancer cells with a blue dye that becomes chemically "charged" in response to light, along with the plant hormone. 

The blue dye absorbs the red light to transfer chemical energy to the plant hormone. 

The hormone then shatters to produce free radicals. 

These form poisonous by-products which can kill cancer cells. 

Professor Peter Wardman, who led the study for Cancer Research UK, said: "Overcoming this oxygen problem is a major challenge in cancer therapy. 

"So far we have shown this works with cells in dishes, but because both the dye and the plant hormone are known to be non-toxic in man, we are hopeful that we can quickly translate this treatment into clinical reality." 

He told BBC News Online: "So far, we have used cells in petri dishes, although I am confident it's applicable to a wide variety of cancer cells, not just specific types. 

He said more research would be carried out with a team from University College London. 

Targeting tumours

Sir Paul Nurse, chief executive of Cancer Research UK, says: "This is fascinating work in that it combines using clever technology with something provided by nature ­ the plant chemicals. 

"It is a further step in the direction of producing a therapy that directly targets the tumour." 

The research is published in the journal Cancer Research. 

 

By Jonathan Amos  BBC News Online science staff in Denver

If the water-ice hidden just below the Martian surface were to melt, it would create a planet-wide sea ankle-deep, scientists have said. 

The latest findings from the Mars Odyssey spacecraft now in orbit around the Red Planet were released here at the annual meeting of the American Association for the Advancement of Science (AAAS). 

The spacecraft's instruments have been trained on the Martian soil for nearly a year. 

Evidence of recent running water?

The data collected has allowed researchers to complete their first global map of where hydrogen (a signature for water) is hidden just below the planet's surface. 

"It's become increasingly clear that Mars has enough water to support future human exploration," said Bill Friedman, whose Los Alamos National Laboratory runs the neutron spectrometer on Odyssey. 

"In fact, there's enough to cover the entire planet to a depth of at least five inches [13cm], and we've only analysed the top few feet of soil." 

The map shows that from 55 degrees latitude to the poles, Mars has extensive deposits of soil that are rich in water-ice, bearing an average of 50% water by mass. 

In other words, one kilogram of soil would yield half a kilo of water if it were baked in an oven by, for example, astronauts who needed drinking water to sustain themselves on the planet. 

The Los Alamos instrument detects neutrons generated when cosmic rays slam into the atoms that make up the Martian soil. Different atoms give off neutrons with specific energies. 

River valleys

By looking for the signature of hydrogen - a major constituent of water molecules - Odyssey can infer the presence of water-ice near the poles and hydrated minerals in lower latitudes. 

These are exciting times for Mars researchers. There are good indications that, on occasions, water still runs across the surface of the planet. 

The Mars Global Surveyor spacecraft, which has been in orbit much longer than Odyssey, has detected what look like channels and river valleys. 

The data all support the current theory that the Martian surface was once wetter and warmer than it is now. 

Dr Maria Zuber, of the Massachusetts Institute of Technology, told the BBC: "People are now starting to think it's possible that Mars might have even had twice as much water initially when it accreted than the Earth did and that's very exciting indeed." 

Researchers have yet to explain satisfactorily where all the water went. If much of it now appears to be in sub-surface soils, they need to work out how it got there. 

Professor Bruce Jakosky, of the University of Colorado told the AAAS: "Mars meets all the environment requirements to be able to support life: liquid water, availability of all the elements out of which you would construct life and a source of energy that could be able to support metabolism. 

"That doesn't prove there's life on Mars but it says it's plausible and not a stupid idea to go and look." 

The US and European space agencies are preparing to launch landers to the planet later this year. 

 

By Richard Black  BBC science correspondent in Denver

A group of leading scientific journals has announced measures aimed at restricting the publication of research which could be used by bioterrorists. 

In a joint statement, the journals' editors say it is crucial that concerns over terrorism do not affect the release of valuable medical research. 

But they say they recognise there may be occasions when new research data should be withheld from publication because it could be abused. 

The statement was released at the annual meeting of the American Association for the Advancement of Science (AAAS) in Denver. 

Balancing act

The statement, signed by 32 editors of scientific journals, is a response to the events of 11 September, 2001, and the anthrax letters that followed. 

In the United States especially, there have been calls from some politicians for draconian restrictions on research; but the editors, including Ronald Atlas, President of the American Society of Microbiology, believe this would create other, perhaps bigger problems for society. 

"We work towards public health and if we slow down the pace of our research, people will die. 

"On the other hand, we are revealing the potential targets by which terrorists could attack us. So it's a very careful balancing act; it's one we absolutely have to get right." 

Special board

All research submitted to journals is reviewed for scientific accuracy before it is published. 

What the journals are now doing is amending this process to include an assessment of the security implications of publication. This could lead to part or all of a paper being withheld. 

The editors write in their statement: "We recognise that on occasion an editor may conclude that the potential harm of publication outweighs the potential societal benefits. 

"Under such circumstances, the paper should be modified, or not be published." 

Mr Atlas said two papers from the 11 journals produced by the American Society of Microbiology had been modified in this way. 

The prestigious journal Science, which is published by the AAAS, has set up a special board to review the security implications of papers that come its way. 

Everyone involved acknowledges the publication restraint is only part of the answer - there is nothing to stop scientists simply posting their research on the internet, for example. 

But as one editor put it here, it marks a philosophical change for science, the end of an age of innocence. 

 

By Christine McGourty  BBC science correspondent in Denver

Infrasound - low-frequency sound beyond the scope of the human ear - is providing scientists with a new way of detecting tornadoes, incoming asteroids and erupting volcanoes. 

Some [volcanoes] are operatic. Others have no singing talent whatsoever, Milton Garces, University of Hawaii

The researchers working in the field reviewed their progress at the American Association for the Advancement of Science (AAAS) annual meeting in Denver. 

They have been the beneficiaries of a £20m global infrasound network that was originally intended to help verify the Comprehensive Nuclear Test Ban Treaty. 

But atom bombs are not the only things the soon-to-be-completed 60 monitoring stations of the network will listen in on. 

There are important spin-offs for scientists who want to use the technology to devise new ways of detecting potentially hazardous, large-scale natural events. 

Growing network

Infrasound consists of sound waves in frequencies below about 20 Hertz - out of the range of what humans can pick up. 

The waves have enormously long wavelengths, measured in kilometres, and are poorly absorbed. Infrasound waves triggered by a large asteroid impact high in the atmosphere, for example, can be detected travelling as many as five or six times around the globe before dissipating. 

Douglas Christie, president of the technical secretariat of the Test Ban Treaty Secretariat in Vienna, Austria, said 15 infrasound monitoring stations were already fully operational and 16 more were under construction. 

The aim is to establish stations uniformly across the globe - countries already hosting a "listening" station include Germany, Canada, Brazil, Paraguay, Australia, Madagascar, the USA, Greenland and Antarctica. 

"The network will very reliably detect even very small nuclear explosions at any point on the globe," he said. "But we also detect infrasound from a large number of other geophysical events. 

"We've detected a large number of exploding meteors - we can also monitor volcanic eruptions very well, even at great distances." 

Civil aviation authorities have asked the treaty secretariat to provide data from the infrasound network to help them detect volcanic eruptions in remote areas and provide early warning to pilots of hazardous emissions. 

Researchers in Hawaii are using infrasound to help them monitor the behaviour of active volcanoes. 

'Singing volcanoes'

Milton Garces, of the University of Hawaii, said each volcano could be said to have its own "voice". "Some are operatic. Others have no singing talent whatsoever," he said. 

"We're developing the ability to understand the language of volcanoes, and translate that into something we can use to forecast an eruption." 

At the National Oceanic and Atmospheric Administration (Noaa) in Boulder, Colorado, scientists are building a prototype infrasound network to provide early warning of tornadoes. 

It is being established in parts of Colorado, Nebraska, Wyoming and Oklahoma. 

The infrasound detectors commonly used consist of ultra-sensitive "micro-barometers", picking up changes in pressure associated with the sound waves. 

Mr Christie said they were "the most sensitive pressure devices ever made". As you go up in the atmosphere, the pressure goes down, he added. 

"Our micro-barometers are so sensitive they can measure the pressure difference between the top and bottom of a single piece of paper." 

At least five Palestinians have died in an unexplained blast in southern Gaza City, witnesses and hospital officials say. 

Representatives of the militant group Hamas said the dead were Hamas activists. 

I heard the sound of screaming women Palestinian neighbour

Several other people were injured in the explosion, which came a day after Hamas militants blew up an Israeli tank in the north of the Gaza Strip, killing its crew of four. 

In the West Bank, two other Palestinians died in clashes with the Israeli army on Sunday as it arrested a senior member of the Palestine Liberation Organisation in the town of Nablus. 

No reason was given for the arrest. 

Militant's house

The Gaza blast occurred on Sunday afternoon local time near the home of a Hamas activist in the al-Zeitun area, known as a Hamas stronghold. 

"I heard the sound of screaming women, and cars evacuating people from the house. I saw at least three people covered in blood being taken away," a neighbour said. 

Reuters news agency said a car laden with explosives had blown up on a farm, but there is no confirmation. 

The Israeli army refused to comment on the blast, fuelling speculation that it could have been part of its expected response following the tank attack on Saturday. 

However according to the Associated Press news agency, Hamas prevented journalists from inspecting the site. 

Correspondents point out that there have been several cases in the past where Palestinian militants have accidentally blown themselves up while manufacturing bombs. 

Following the attack on the tank, Israeli Defence Minister Shaul Mofaz told a weekly cabinet meeting his troops would hit hard at Hamas in Gaza. 

"Israel will land a serious blow against the Hamas infrastructure in the Gaza Strip," he said, quoted by the AFP news agency. 

In Nablus, two Palestinians were killed and nearly 30 wounded by army fire in a clash between soldiers and Palestinian gunmen and stone-throwers. 

One of the wounded was in a coma and on life support, hospital officials said. 

The clashes erupted as Israeli troops and tanks moved into the centre of the town to arrest Taysir Khaled, a member of the PLO executive committee. 

Iran says it has arrested and deported more than 500 people suspected of links to al-Qaeda. 

But it said it had no information that al-Qaeda leader Osama Bin Laden's eldest son was in the country after fresh reports emerged of his presence there. 

We will arrest Bin Laden's son if he is in Iran  Foreign Minister  Kamal Kharrazi

However if Saad Bin Laden did turn out to be in Iran, action would be taken, Foreign Minister Kamal Kharrazi told a Tehran news conference. 

The US has repeatedly accused Iran of harbouring al-Qaeda members - allegations Tehran has strenuously denied. 

Porous border

Iran "will never be a sanctuary for members of al-Qaeda," Mr Kharrazi told journalists. 

He said Iran's current policy "towards those suspected of links with al-Qaeda" is to arrest them and expel them to the country from which they arrived, or to their country of origin. 

Kharrazi: Policy is to crack down on al-Qaeda

He did not say when or over what period of time the arrests and deportations took place. 

Last August, Tehran announced it had deported 12 Saudi men suspected of being al-Qaeda members back to Riyadh. 

They were thought to have taken refuge in Iran after the US began military action in Afghanistan to rout the former Taleban leaders and al-Qaeda associates. 

Iran has acknowledged that some fleeing al-Qaeda members have been able to slip into the country, which has an extensive eastern border with Afghanistan. 

Persistent reports

In the last week or so, press reports quoting diplomatic and US intelligence sources have suggested that Saad Bin Laden is currently in Iran 

"Allegations about Bin Laden's son are not new," Mr Kharrazi said. 

"Definitely we will arrest him if he is located in Iran." 

CIA director George Tenet last week said al-Qaeda members fleeing Afghanistan had established a presence in Iran and Iraq. 

Saad Bin Laden, who is about 23 years old, is believed to be the oldest of more than 20 children the al-Qaeda leader has by several wives. 

US intelligence officials believe Saad Bin Laden has begun to play a prominent role in al-Qaeda since the group went into hiding after leaving Afghanistan. 

The Israeli Government has announced that it will allow the immigration of another 20,000 Ethiopians of Jewish origin. 

Most of them are from the Falash Mura community, who were originally Jewish, but were forced to convert to Christianity in the 19th Century. 

The last mass immigration of Ethiopian Jews was in 1991, when Israel organised a dramatic airlift of 15,000 people who had fled fighting at the end of Ethiopia's civil war. 

15,000 Jews were airlifted from war-torn Ethiopia in 1991

Israel had previously rejected requests for this new group to immigrate. But following the U-turn by the Israeli Cabinet at its weekly meeting, officials will now be sent to Ethiopia to organise the move. 

The move to allow the Ethiopians - 17,000 Falash Mura and 3,000 so-called Falashas - into the country was led by the religious Shas party, which holds the interior ministry. 

The BBC's Jerusalem correspondent James Reynolds says that previous immigration attempts by the Falash Mura have been hampered the fact that they have largely been unable to prove they are Jewish. 

The Ethiopians have been trying to use the "right of return" - an Israeli law which allows Jews from anywhere in the world to obtain automatic Israeli citizenship. 

Discrimination 

In January 3,000 Ethiopian immigrants demonstrated outside Prime Minister Ariel Sharon's office to urge the government to allow their relatives to join them even if they could not prove they were Jewish. 

The protesters held up pictures of their relatives left behind in Ethiopia, claiming they were "victims of discrimination". 

Now Shas has decided that the community has retained its Jewish makeup - that it only converted to Christianity out of fear. 

The party has persuaded the cabinet that those who so desire should be allowed to settle in Israel. 

About 80,000 Ethiopian Jews already live in Israel. Our correspondent says they remain one of the poorest sections of Israeli society. 

Many of them have ended up living in the occupied West Bank and they suffer from a hi