More than 5,000 people have been killed during the Syrian government's violent crackdown on pro-democracy protesters, the United Nations has said.
UN High Commissioner for Human Rights Navi Pillay told the Security Council on Tuesday that President Bashar-al Assad's regime should be referred to the International Criminal Court for crimes against humanity.
Inspired by the Arab Spring uprisings across the Middle East, protesters took to the streets of Syrian cities in March to call for greater democratic freedom.
Assad's regime responded with months of attacks on civilians in an attempt to crush the opposition movement.
Pillay told diplomats at the UN that the estimated death toll had now passed 5,000, including more than 300 children. As recently as 8 November the UN said the death toll stood at 3,500, indicating the violence has increased in intensity.
Pillay told the Security Council that "independent, credible and corroborated accounts demonstrate that these abuses have taken place as part of a widespread and systematic attack on civilians".
CNN reports that Britain's ambassador to the UN, Mark Lyall Grant, said the human right's chief's briefing was "really distressing".
"It was the most horrifying briefing that we have had in the Council in the last two years," he said.
Speaking at a joint press conference with US Secretary of State Hillary Clinton in Washington on Monday, Foreign Secretary William Hague said both Britain and the US shared a "growing concern" about the "deplorable violence" in Syria.
"We welcome the continued efforts of the Arab League and call on the international community to unite in its condemnation of events in Syria," he said.
President Assad recently denied he was responsible for the deaths at the hands of the military: "I did my best to protect the people," he told ABC's Barbara Walters during an interview in Damascus. "You feel sorry for the life that has been lost, but you don't feel guilty when you don't kill people."
"They're not my forces," Assad said when asked if Syrian troops were responsible for killing demonstrators. "They are military forces (who) belong to the government. I don't own them. I'm president. I don't own the country."