The United Nations High Commissioner for Human Rights says more than 2200 people have been killed in a crackdown on anti-government protests since the middle of March in Syria.
The previous United Nations toll was between 1900 to 2000.
The UN Human Rights Council held an urgent session on Monday on the situation when the new toll was advised by Human Rights High Commissioner Navi Pillay.
''The military and security forces continue to employ excessive force, including heavy artillery, to quell peaceful demonstrations and regain control over the residents of various cities,'' she said.
The meeting of the UN Human Rights Council was called by 24 states, including Jordan, Kuwait, Saudi Arabia and Qatar.
Syria's ambassador to the UN defended his government and dismissed the allegations as ''mere lies''.
''The resolution will only cause the crisis to lengthen and will only cause more instability,'' said Faysal Khabbaz Hamoui.
President Bashar al-Assad said on Sunday that his government was in no danger of falling.
And he warned that any foreign military intervention would backfire on those who carry it out.
The BBC reports he said the solution in Syria was a political one, but added that steps were being taken to introduce a multi-party system and elections might be held in February.