Two explosions have struck Aleppo University in northern Syria, killing at more than 80 people, official sources and opposition activists say.
There were conflicting reports as to what caused the blast on Tuesday, with the government and opposition blaming each other.
The explosions set cars ablaze and blew the walls off dormitory rooms.
The UK-based Syrian Observatory for Human Rights cited students and medical officials as saying that 83 people were killed in the explosions near the university's dorms. More than 150 people were injured, several of them in critical condition, the group said, without giving details about the cause of the explosions.
Other anti-regime activists said missiles fired by government jets caused the blasts. A witness told Al Jazeera that she saw bombs falling from the sky.
Bashar Jaafari, Syria's envoy to the United Nations, called the attack "a cowardly terrorist act that targeted the students of Aleppo University as they sat for their midterm examinations."
Meanwhile, state television said two rockets hit the university, killing students and people who had fled fighting elsewhere in recent months and taken refuge on the campus grounds. It blamed rebels for the attack.
Mohammed Wahid Akkad, the governor of the city, gave similar casualty figures to those cited by the Observatory.
"So far there are 82 fatalities and more than 160 wounded in a terrorist attack that targeted students on their first day of exams at the University of Aleppo," Akkad told the AFP news agency.
As well as students, the campus houses about 30,000 people who have fled homes in areas of the city ravaged by fighting since July last year.
A military official in Aleppo told AFP that the explosion occurred after rebels tried to shoot down a warplane with a missile, but failed to hit their target.
Fighting between rebels and government forces has reached a stalemate in Aleppo and left the city divided. The university is located in an area under government control. Government troops and rebels frequently exchange rockets and mortar rounds in the city.
Over recent months, Aleppo and the capital, Damascus, have been hit by a wave of explosions that have killed scores of people. Many of the bombings, which have largely targeted government buildings, have been claimed by groups fighting to overthrow President Bashar al-Assad.
Elsewhere in Syria, troops and rebels fought in embattled suburbs of Damascus on Tuesday, as government air raids and shelling in the other regions killed several dozen people, activists said.