More than 80 people have been killed by two blasts in the northern Syrian city of Aleppo, activists and officials say. The explosions reportedly struck an area between the University of Aleppo's halls of residence and the architecture faculty on the first day of exams. The Syrian Observatory for Human Rights put the death toll at 83, and Aleppo's governor said 82 people had died. State TV said "terrorists" had launched rockets at the campus, but activists blamed missiles fired by warplanes. In almost two years of fighting in Syria, Aleppo has been the scene of intense conflict between government and opposition forces. However, neither side has been able to force the other to retreat for good, says the BBC's James Reynolds in neighbouring Turkey. Video footage of the aftermath of the explosions in Syria's second city showed the facade of one of the university residences blown away. Burned-out vehicles and bodies could be seen on the street outside, while tearful survivors were shown taking refuge in a nearby building. The Syrian Observatory for Human Rights, a UK-based activist group, said at least 83 people had been killed and 150 injured, with some in a critical condition. It said there were "conflicting reports of air raids and two explosions on the ground". The SOHR has emerged as one of the most prominent organisations documenting and reporting incidents and casualties in the Syrian conflict. The group says its reports are impartial. The governor of Aleppo, Mohammed Wahid Akkad, told the AFP news agency that so far 82 had died and 160 were wounded. He blamed a "terrorist attack that targeted students on their first day of exams". The state news agency, Sana, said the victims included students and people displaced by the fighting who had taken shelter in the halls of residence and faculty building. The education minister called for a nationwide day of mourning on Wednesday and said President Bashar al-Assad had ordered the "immediate rebuilding of damaged parts of the university". A military source told AFP that a stray surface-to-air missile fired by rebels had hit the campus, which lies in a government-controlled area of the city. The nearest rebel-held area is more than a mile away. However, no rebel group has said it was behind the blasts, and opposition activists said government had sent fighter jets to bomb the campus. The Local Co-ordination Committees (LCC), an opposition activist network, posted a link to an online video which purported to show warplanes bombing the campus. It showed students walking quickly away from the university after the first explosion. The camera then shakes to the sound of another explosion and people begin running. "The warplanes of this criminal regime do not respect a mosque, a church or a university," a student who gave his name as Abu Tayem told the Reuters news agency. Rebels have previously carried out bombings against government targets in Aleppo. In October, at least 34 people were killed in a series of bombings in the city's main square. Activists also reported fierce fighting between the rebel Free Syrian Army (FSA) and government forces in two districts of the capital, Damascus. The clashes erupted in Ain Tarma and Zamalka after a series of air strikes on rebel positions over the past few days. The LCC also said as many as 62 people had been killed by government forces in Homs province, most of them in the Houla and Bahsariya areas. It put the nationwide death toll on Tuesday at 218, including 96 in Aleppo. The United Nations says more than 60,000 people have been killed since the uprising against President Assad began in March 2011. Prime Minister Wael al-Halaqi arrived in Iran's capital, Tehran, on Tuesday to discuss Mr Assad's "three-step plan" for resolving the conflict with senior officials, the Fars news agency reported. Meanwhile, Russia's foreign ministry rejected a request from more than 50 countries to have the UN Security Council refer Syria to the International Criminal Court, calling it "ill-timed and counterproductive".