By RICK GLADSTONE and HWAIDA SAAD

Published: January 15, 2013

At least two deadly explosions possibly caused by aircraft missiles or bombs devastated the campus of Aleppo University in Syria on Tuesday as students were taking exams, a major escalation of the violent struggle for control of the country’s largest city. The opposition and government blamed each other for the blasts, among the worst since the Syrian conflict began nearly two years ago.

Syria’s ambassador to the United Nations, Bashar Jaafari, said at a Security Council meeting that 82 people were killed and 192 wounded in the explosions, which he called a terrorist attack, the Syrian government’s blanket terminology for the armed insurgency against President Bashar al-Assad. Opposition sympathizers said more than 50 people were killed.

The university’s own press office appeared to have issued a statement accusing Syrian Air Force MIG fighter planes of targeting the campus in two missile attacks three minutes apart, destroying buildings and causing “massive destruction in the surrounding roads.” The statement denounced the attacks as a “criminal act.” But it was unclear if the statement, which was posted on an opposition Facebook page, reflected the view of the leadership of the public university, which is in a government-controlled part of the city.

Aleppo, in northern Syria, has essentially been under siege since July, with insurgents and government forces in a stalemate. Once the commercial epicenter of Syria, Aleppo has been struck by numerous shellings, bombings and airstrikes. But the university has been conducting classes and trying to provide some appearance of normalcy despite the mayhem and deprivation that have ravaged other parts of the city, and the campus area had been largely spared until Tuesday.

Activists also reported that violence convulsed some suburbs of Damascus, the capital, where members of the insurgent Free Syrian Army were engaged in combat with government forces in the Ain Tarma and Zamalka neighborhoods. The fighting erupted after a campaign of Syrian Air Force attacks over the past few days apparently aimed at expunging insurgents from strategic areas.

The Syrian Observatory for Human Rights, an antigovernment group based in Britain with a network of contacts in Syria, reported a death toll of 52 and dozens of injuries in the explosions at Aleppo University, while Syria’s state-run SANA news service did not specify the number of casualties but said the explosions came on the first day of exams. SANA attributed the death and destruction to at least two rockets fired by an unspecified “terrorist group.”

Competing and contradictory accounts of what happened proliferated as news of the explosions spread, none of them verifiable because of the difficulties of firsthand reporting inside Syria.

The Syrian Observatory, for example, said bombs in booby-trapped cars might have been responsible. Others said the blasts might have been caused by Scud missiles, which Mr. Assad’s forces have used before on military targets. Some witnesses reported hearing the screech of warplane jet engines, but there was no corroborating video. Others reached by phone said that both sides in the conflict were to blame.

According to one student, insurgent fighters just outside Aleppo who apparently were armed with a heat-seeking missile fired it at a MiG fighter, the pilot dropped a heat balloon as an evasive tactic, the missile followed the balloon, and then exploded near a military post adjacent to the university dormitories. That account, however, did not explain the second explosion.

Others also reported seeing what they described as heat balloons before the explosions. Some said the university dormitories, which were housing students and civilians displaced by fighting elsewhere, were hit by one missile, and that other missiles struck the buildings that house the university’s architecture and humanities departments.

The Syrian National Council, a member of the anti-Assad coalition, accused Mr. Assad’s government of responsibility. “The regime used heavy weapons to bombard Aleppo University students while taking their exams, killing dozens of them,” it said in a statement. “By committing unprecedented heinous atrocities, the regime hopes to see hatred and destruction in Syria before its demise.” Witness accounts and videos uploaded on the Internet from the campus and a nearby hospital painted a picture of utter panic as the explosions shattered an examination day with billowing smoke, fire and showers of fragmented concrete and glass.

“I was inside my car when I heard the sound of two consecutive explosions, which was preceded by the sound of a warplane,” said an antigovernment activist in Aleppo reached on his mobile telephone, who identified himself only by his first name, Tony, for security reasons. “There was a mess on the street created by the traffic. I saw smoke coming from dormitories. It was surprising to see the university being bombed.”

An education student who identified himself as Abu Tayem in a Skype conversation said he had finished his exams at 10:30 a.m. and left campus, and that a friend called in tears a few hours later with the news: “I rushed immediately to see what happened. I saw blood, flesh littered all around; the most painful scene was a chopped hand with a pen and notebook right next to it. I saw two female students crying, they were speechless. I tried to convince them to return home; they were crying nonstop.”

He also described what he called “two big holes, caused by two missiles,” in what had been a campus square. “I could not see it any more, it’s vanished,” he said. The United Nations has estimated that more than 60,000 people have been killed in Syria since the uprising against Mr. Assad began in March 2011.

Mr. Assad appeared to further distance himself on Monday from any thought of relinquishing power via a BBC interview with his deputy foreign minister, Faisal Muqdad. Mr. Muqdad suggested that Mr. Assad would run for re-election next year when his term expires. “We are opening the way for democracy, or deeper democracy,” he said. “In a democracy you don’t tell somebody not to run.”

Groups opposed to Mr. Assad have said they will not even consider political dialogue to resolve the conflict unless Mr. Assad resigns or is removed from power first. The special peace envoy from the United Nations and the Arab League, Lakhdar Brahimi, has urged Mr. Assad to step down and said he cannot be part of any transitional government. The Syrian government has accused Mr. Brahimi of bias toward the insurgency.

With diplomacy still deadlocked, more than 50 member states in the United Nations submitted an unusual written appeal to the Security Council on Monday to at least request an investigation by the International Criminal Court into possible war crimes and atrocities committed in Syria, by both the loyalist and the insurgent sides.

But whatever chance of such a move appeared to be ended on Tuesday by Russia, the biggest foreign defender of the Syrian government, which has vetoed three Security Council proposals on Syrian intervention since the conflict began.

“We consider this initiative ill-timed and counterproductive if we are to achieve the current priority goal — an immediate end to bloodshed in Syria,” Russia’s Foreign Ministry said in a statement. “We are convinced that speculation about international criminal prosecution and the search for guilty parties will only serve to keep the opposing sides in hard-line positions and complicate the search for a path of political-diplomatic settlement of the Syrian conflict.”

Rick Gladstone reported from New York, and Hwaida Saad from Beirut, Lebanon. Reporting was contributed by Hania Mourtada from Beirut, Ellen Barry from Moscow, and Neil MacFarquhar from the United Nations.