Supporters of Venezuelan President Hugo Chavez have clashed with university students who were planning an anti-government demonstration in Caracas.
Witnesses say the incident happened Thursday, when the pro-Chavez activists attacked the students at the state-funded Central University of Venezuela.
The witnesses also say the government supporters stoned television crews who arrived at the school to cover the event. At least one person was injured in the skirmish.
Metropolitan police officers stayed outside the grounds of the university. Venezuelan law prohibits police from entering universities without authorization from those schools.
Tensions have risen in the oil-rich country in recent months as President Chavez's opponents step up calls for his resignation.
On Thursday, government officials said a military officer who called for the president to step down was ordered to resign.
Defense Minister Jose Vicente Rangel said officials decided to discharge Air Force Colonel Pedro Soto for inciting anti-government protests. Colonel Soto, however, says he will challenge the decision, saying the nation's constitution allows freedom of expression.
The colonel called for Mr. Chavez's resignation two weeks ago, saying the Venezuelan leader threatens democracy. Two other military officials have spoken out publicly against Mr. Chavez. The president has dismissed the criticism, saying Venezuela is not facing a "military rebellion."