Syrian activists say the death toll in two blasts inside the campus of the main university in the northern city of Aleppo has risen to 83.
The Britain-based Syrian Observatory for Human Rights says some of the more than 150 injured in Tuesday's blast (local time) are in critical condition.
It said the dead included university students and civilians staying in the university dormitories after being displaced by fighting between forces loyal to President Bashar Assad and rebels seeking to topple his regime.
Bloodshed has disrupted civilian life across Syria since a violent government crackdown in early 2011 on peaceful demonstrations for democratic reform turned the unrest into an armed insurgency bent on overthrowing President Bashar al-Assad.
More than 50 countries asked the United Nations Security Council to refer the crisis to the International Criminal Court, which prosecutes people for genocide and war crimes. But Russia - Assad's long-standing ally and arms supplier - blocked the initiative, calling it "ill-timed and counterproductive".
Each side in the 22-month-old conflict blamed the other for the blasts on Tuesday (local time) at the University of Aleppo, located in a government-held area of Syria's most populous city.
Some activists in Aleppo said a government attack caused the explosions, while state television accused "terrorists" - a term they often use to describe the rebels - of firing two rockets at the school. A rebel fighter said the blasts appeared to have been caused by "ground-to-ground" missiles.
Early today (NZT) the observatory said at least 52 people were killed and dozens wounded, but it could not identify the source of the blasts.
"Dozens are in critical condition. The death toll could rise to 90," the observatory said in a statement, citing doctors and students.
State television - which did not give a death toll - showed a body lying on the street and several cars burning. One of the university buildings was damaged.
Video footage showed students carrying books out of the university after one of the explosions, walking quickly away from rising smoke. The camera then shakes to the sound of another explosion and people begin running.
If confirmed, the government's report of a rocket attack would suggest rebels in the area had been able to obtain and deploy more powerful weapons than previously used.
The nearest rebel-controlled area, Bustan al-Qasr, is more than a mile away from the university.
Activists rejected the suggestion that insurgents were behind the attack, however, and instead blamed the government.
"The warplanes of this criminal regime do not respect a mosque, a church or a university," said a student who gave his name as Abu Tayem.
GRINDING TOWARD STALEMATE
The rebels have been trying to take Aleppo - once a thriving commercial hub - since the summer, but have been unable to uproot Assad's better-armed and more organised forces.
International efforts to find a political solution to Syria's civil war have similarly resulted in stalemate, even as the conflict's death toll has surged above 60,000.
The crisis has driven hundreds of thousands of people to flee the country, many to neighbouring Jordan, Lebanon and Turkey, where a fire at a camp in the country's southeast killed a pregnant Syrian woman and her three children on Tuesday.
Inside Syria, neither the military nor the insurgents have been able to sustain clear momentum.
The rebels remain poorly equipped and disorganised compared with Assad's forces, despite winning support from some regional powers like Turkey and Saudi Arabia.
The government also benefits from superior air power, used to pummel rebel-held areas around Damascus and elsewhere.
Rebel efforts to assault the capital also appear to have ground towards an stalemate. A witness in a rebel-controlled district of Damascus said on Tuesday the front line between the two sides was quiet.
The streets were still full of civilians, the witness said, despite the sound of shells hitting nearby buildings. He said people were walking around, buying sweets and sandwiches.