At least 82 people are reported to have been killed in two explosions at Aleppo University in Syria.
Syria's UN Ambassador Bashar Ja'afari described the incident as "a cowardly terrorist act" on students sitting for exams in Syria's biggest city.
"This act killed 82 students and wounded 162 other students," he told the UN Security Council during a debate on counterterrorism.
A Syrian opposition group put the death toll from the two explosions that rocked the university at 83.
The cause of the explosions was not clear, but the Syrian government and opposition activists blamed each other.
"The terrorist armed groups in my country always take advantage of a security council meeting to perpetrate a terrorist attack inside Syria and this is indeed what happened today perhaps for the tenth or 20th time since the crisis in my country began," Mr Ja'afari told the 15-nation council.
According to the United Nations, more than 60,000 people have been killed during a 22-month revolt against Syrian President Bashar al-Assad, which began with peaceful protests but turned violent after Mr Assad's forces tried to crush the demonstrations.
UN special envoy for Children and Armed Conflict, Leila Zerrougui, said more than 20 children had been killed and many injured during the past few days in air strikes and other attacks on populated areas in and around Damascus.
"Children pay a very high price in the ongoing fighting. All parties must immediately refrain from targeting civilian areas and take all necessary precautions to protect girls and boys," she said in a statement.
In a letter to the Security Council and UN Secretary-General Ban Ki-moon, dated 9 January, Mr Ja'afari outlined details of a peace plan put forward by Mr Assad in a speech earlier this month.
Although Mr Assad's speech appeared to dismiss peace talks with his enemies and was rejected by opposition groups, Mr Ja'afari wrote that the government was prepared to enter a national dialogue in an attempt to resolve the crisis.
In preparation for such a dialogue, Mr Ja'afari said all countries in the region should stop funding, arming and harbouring rebels, while all combatants - government forces and rebel fighters - should adhere to a ceasefire.
He said: "Guarantees will be offered to Syrian opposition groups in order that they might enter the country, without conditions, to participate in the national dialogue."
More than 50 countries asked the security council to refer the Syria crisis to the International Criminal Court, which prosecutes people for genocide and war crimes.
However, Russia, which is Mr Assad's long-standing ally and a major arms supplier, blocked the initiative, calling it "ill-timed and counterproductive".