More than 5,000 people have died in the nine-month-long Syrian uprising, UN human rights chief Navi Pillay said on Monday.
Pillay, the UN high commissioner for human rights, told reporters on Monday that she told security council members of the dramatic increase in deaths during an afternoon briefing.
The death toll used by the UN in recent weeks has been around 4,000.
Pillay said she recommended that the council refer Syria to the International Criminal Court, the permanent war crimes tribunal, for investigation of possible crimes against humanity.
Pillay said that at least 300 children are among the dead, and there are thousands of people in detention.
She noted that the last time she briefed the council on Syria, in August, the death toll was at about 2,000.
US ambassador Susan Rice said Pillay’s briefing “underscores the urgency of the present moment.”
"Through condemnations issued by the UN general assembly and human rights council and bold steps taken by the Arab League and the government of Turkey, international bodies are starting to match their severe disapproval of Syria’s bloody crackdown with concrete steps to bring it to an end," Rice said.
"It is past time for the UN security council to do the same."
The representatives of France, Britain and Portugal also said it was time for the council to take strong action on Syria.
Last month, Russia and China vetoed a western-backed UN security council resolution condemning the bloodshed in Syria.
"The only way to resolve the situation in Syria is through a Syrian-led political process, and that means dialogue," Russian ambassador Vitaly Churkin said.