At least seven children were among the scores killed in an airstrike near the Syrian capital of Damascus over the weekend, according to reports.
The Britain-based Syrian Observatory for Human Rights said the dead were killed by government air artillery strikes in the eastern Ghouta district, the Associated Press reported.
That report placed the total death toll at 34, while Reuters — citing opposition activists — reported that at least 36 were killed, including as many as 14 children.
Abdel Rahmanthe director of the Syrian Observatory told Agence France-Presse "the children were aged between six months and 9 years old."
Five women were also killed in the strike, he reportedly said.
The Observatory said Sunday's bombardment was one of the heaviest of the 22-month-old conflict.
According to Reuters, video footage emerged purporting to show women weeping over the dismembered bodies of children in a field near the town of Muleiha, 3 miles east of the capital.
On Monday, more than 50 countries called on the United Nations Security Council to refer the Syria conflict to the International Criminal Court.
"We are firmly of the view that the Security Council must ensure accountability for the crimes that seem to have been and continue to be committed in the Syrian Arab Republic and send a clear signal to the Syrian authorities," read the letter, sent by Switzerland on behalf of more than 50 nations, according to Reuters.
"The situation on the ground has only become more desperate, with attacks on the civilian population and the commission of atrocities having almost become the norm," the letter said. It was supported by permanent council members France and Britain.
Syria's army has reportedly been moving to take back key rebel-held territory in towns near Damascus in recent weeks.
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The rebels overran a military base near Damascus two months ago, coming close to the main international airport; Muleiha reportedly has an air defense base, but Reuters did not specify if they were the same.
The Observatory, which relies on reports from a network of activists as well as doctors and lawyers inside Syria, has estimated that more than 3,500 children have been killed in the conflict.
Citing UN figures, AFP reported that more than 60,000 people had been killed in Syria since the start of an uprising against President Bashar al-Assad in March 2011.