More than 191,000 people have been killed in the Syrian conflict up to April, the UN human rights chief says.
Navi Pillay said the figure was "probably an underestimate" and criticised what she called "international paralysis" on the issue.
The figure is more than double the UN estimate given a year ago.
Opposition groups in Syria have been fighting President Bashar al-Assad for over three years, but have lost ground in recent months.
The UN report was based on data from four different monitoring groups and the Syrian government which was then cross-checked.
"Tragically it is probably an underestimate of the real total number of people killed during the first three years of this murderous conflict", Mrs Pillay, the UN High Commissioner for Human Rights, said.
"The killers, destroyers and torturers in Syria have been empowered and emboldened by the international paralysis" she added.
The highest number of killings was recorded in Damascus province, with 39,393 deaths, followed by Aleppo, with 31,932.
Both the Syrian government and Syrian rebel groups have been accused of war crimes by the UN.
Syria, Iraq and Islamic State
One year on from the chemical weapon attack in Damascus, the war in Syria has become part of a wider regional struggle.