Twin blasts ripped through university buildings in Syria's second city Aleppo on Tuesday killing at least 83 people and wounding scores more, on the first day of exams for students.
Regime forces and rebels blamed each other for the carnage, in a government-controlled area of the battleground northern city.
"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," Governor Mohammed Wahid Akkad told AFP by telephone.
The Britain-based Syrian Observatory for Human Rights said 83 people had been killed in the blasts and at least 150 others wounded, some critically.
While opposition activists said government jets had carried out an air strike, a military official said ground-to-air missiles fired by rebels had fallen short.
State television said "terrorists launched two rockets" at the campus.
State news agency SANA said "it was the first day of exams. Students and displaced people were among the victims".
As well as students, the university campus houses some 30,000 people who have fled parts of the city ravaged by fighting since rebels seized many neighbourhoods last July.
Some of those displaced people were among the casualties SANA reported, citing an official source.
Video footage posted online by students showed tearful survivors taking refuge in a campus building.
The explosions struck an area near the university dormitories and the architecture faculty, the Observatory said, adding "the nature of the explosions is still unclear.
"There are conflicting reports of air raids and two explosions on the ground."
Nationwide, at least 152 people were killed on Tuesday, 128 of them civilians, the Britain-based watchdog said.
It also said dozens of people had been killed or wounded when Syrian troops stormed rebel positions near a military academy in the central province of Homs Tuesday.
The Syrian Revolution General Council accused regime forces of having "committed a massacre" there, saying "more than 24 people were summarily executed and their homes and bodies were burned".
The latest violence came as Russia rejected as "counterproductive" Swiss-led efforts at the UN Security Council to seek prosecution of key figures in Assad's regime before the International Criminal Court.
Only the Security Council has the right to refer the Syria case to the Hague-based court because Syria is not an ICC member.
Russia, a traditional Syrian ally, has vetoed three prior council resolutions sanctioning Assad. It said Tuesday that a war crimes referral could only escalate the crisis.
Moscow also once again reaffirmed its support for a Syrian transition plan agreed by world powers in June that was never implemented because of the fighting.
It called for the quick creation of an interim government with full powers, but it never assigned a clear role for Assad -- and that issue has been interpreted differently by Russia and the West.
Syrian Prime Minister Wael al-Halaqi arrived in Tehran on Tuesday for talks with Damascus's key regional ally, state television reported.
The Fars news agency said the two sides would discuss "Assad's three-step plan" for the political future, which he presented on January 6.
The opposition and Western governments rejected Assad's plan, saying it was detached from reality. It offered dialogue but only with opposition groups he deemed acceptable, not "terrorists" led by foreigners.
Iran has supplied financial aid to Syria and has confirmed sending military advisers to assist in the regime's nearly 22-month crackdown.
According to UN figures, more than 60,000 people have been killed in the violence in Syria since March 2011.
Washington meanwhile brushed aside a report of a leaked State Department cable indicating that Syria had used chemical weapons during the crackdown.
Foreign Policy, an online magazine, said it had acquired a report by US diplomats in Turkey that made a "compelling case" Damascus had used poison gas.
But National Security Council spokesman Tommy Vietor said there was no evidence Syria had taken new steps towards using chemical weapons.