University leaders accused the Venezuelan government of provoking violence to justify military occupations of campuses where students are leading protests against President Hugo Chavez. Gunmen opened fire on students returning from a peaceful march Wednesday in which 80,000 people denounced a constitutional referendum planned for December that would expand Chavez's power. At least eight people were injured, including one by gunfire, officials said. Higher Education Minister Luis Acuna offered Wednesday to send in troops to quell the violence, but university authorities quickly rejected the offer as an attempted power grab. "We won't fall into the trap," Eleazar Narvaez, rector of the Central University of Venezuela, said Thursday. Chavez opponents say the president has long wanted to end the autonomy of Venezuela's public universities, most of which are run by opposition rectors who defeated Chavista candidates in campus elections. Street demonstrations led by university students have spread to at least six cities around Venezuela, and organizers vowed to continue protesting despite crackdowns by security forces and clashes with government supporters. The marches have been mostly peaceful, although there have been several clashes in which students threw rocks and police shot plastic bullets at demonstrators. On Wednesday, photographers for The Associated Press saw at least four gunmen - their faces covered by ski masks or T-shirts - firing handguns at a crowd of government opponents returning to the Central University of Venezuela from the march. Justice Minister Pedro Carreno blamed students, opposition leaders and the media for the violence. "We want to urge the media to reflect, to stop broadcasting biased news through media manipulation, filling a part of the population with hate," Carreno said in a national address. But faculty president Victor Marquez accused Chavez's government of provoking the violence at Venezuela's largest university by sending in armed Chavista militias. "Pedro Carreno lies by saying students spurred the violence. They know perfectly well where the violence is coming from," Alvarez said at a news conference. He said three pro-Chavez militias - the Colectivo Alexis Vive, Los Carapaicas, and Los Tupamaros - were being encouraged to attack protesters. "These are the ones responsible, the government's paramilitary groups," he said. Washington is watching - and weighed in against the violence on Thursday. "I can't tell you exactly who is responsible for this, but it's just an appalling act and just another indication of the kind of atmosphere that you see in Venezuela," State Department spokesman Sean McCormack said. "These people were expressing themselves in a peaceful manner." Globovision, Venezuela's only private television network that remains openly critical of Chavez, broadcast video of armed men riding motorcycles onto the campus and entering the same building where several gunmen who had shot at the crowd were hiding. The pistol-toting men stood in a doorway - one of them firing a handgun in the air - as people fled the building. Later, state TV showed footage of angry anti-Chavez students - many of them with their faces covered by T-shirts - setting fire to benches and throwing rocks at the university building before the armed men on motorcycles arrived. "The Colectivo Alexis Vive, a group of delinquents paid and armed by the government, was allowed to attack students," student leader Ricardo Sanchez said, according to Thursday's El Universal newspaper. Students met Thursday to plan how to keep up street demonstrations that have spread to the cities of Merida, Maracaibo, Puerto La Cruz, San Cristobal and Barquisimeto. At issue are 69 constitutional amendments, approved for the Dec. 2 referendum by the overwhelmingly Chavista National Assembly, that would let Chavez run for re-election indefinitely, suspend civil liberties during states of emergency, censor the news media and take complete control over the national bank.