At least 350,209 people have been killed in 10 years of war in Syria, the UN says in its first official death toll since 2014.
Its human rights chief cautioned the figure is "certainly an under-count of the actual number of killings".
A leading but unofficial UK-based monitoring group recently put the death toll at over 606,000.
The war in Syria has largely wound down with just a single province now controlled by jihadists and rebels.
At its height in 2015, armed groups had taken over large swathes of the country, but the intervention of Russia in an aerial campaign on the side of Syrian President Bashar al-Assad turned the tide in his favour.
The fighting began in March 2011 when opposition supporters took up arms after security forces opened fire on demonstrators demanding more freedoms under President Assad's authoritarian rule.
The UN officially stopped counting deaths in the conflict in January 2014 because, it said, it had become impossible to accurately document the constantly growing toll, relying as it had been on the co-operation of a diminishing number of non-governmental groups on the ground to do so.
In March this year, when the war reached its tenth year, the UN Human Rights Council (HRC) requested the human rights office resume trying to determine the number of people killed.