Activists: Syrian troops storm university, arrest hundreds At least four people are killed when forces raid a university in northwest Syria, group says Opposition: At least 200 students are arrested The attack comes amid an international outcry over a truce violation The U.N. has 24 observers into the nation, plans to send more (CNN) -- Syrian forces raided a university Thursday, the opposition said, the latest sign of continuing attacks despite a truce implemented three weeks ago and the presence of United Nations monitors in the country. The troops targeted anti-government protesters in Aleppo University, killing four and injuring 28, according to the Syrian Observatory for Human Rights. About 200 students were arrested, the opposition group said. Soldiers also fired at the hospital where the wounded were taken, leading to more casualties, said Mohammad Hareitan, 25, a student at the university. It was unclear how many more people were wounded in those attacks. The reported attacks come despite the presence of U.N. observers, who have reported cases of cease-fire violations from the government and the opposition. U.N. peacekeeping chief Herve Ladsous has declined to say which side accounts for more violations. There are 24 unarmed military observers, with the number expected to increase to 300 by the end of the month, Ladsous said. Observers are in Homs, Hama, Daraa, Idlib and Damascus. The cease-fire went into effect April 12 and is part of a six-point peace plan negotiated by international envoy Kofi Annan. Annan's plan includes allowing humanitarian groups access to the population, releasing detainees, starting a political dialogue, and withdrawal of troops from city centers, a mandate the government has not met, according to the United Nations. "So far, the Syrian regime has taken, really, almost no steps toward fulfilling the core commitments of the Annan proposal," said Mark Toner, the State Department spokesman. Though the United States seeks an end to violence by both sides, most of the attacks have been by the government forces, he said. Syria said Wednesday that it is committed to the peace plan. "We are waiting for Mr. Annan to take tangible steps toward the armed terrorist groups and take commitments from the states which support and sponsor them to halt violence in Syria," Information Minister Adnan Mahmoud said, according to the state-run Syrian Arab News Agency. The government has consistently blamed the violence on "armed terrorists." Syria's protests started peacefully in March last year, but a government crackdown spawned violence that has left thousands dead and prompted some military defectors to take up arms against the regime forces.