The Office of the UN High Commissioner for Human Rights said that as of Tuesday, 1,700 civilians had died in the eastern regions of Donetsk and Luhansk.
It says at least 3,238 civilians, including 227 children, have been killed in Ukraine since the Russian invasion began, according to new figures.
It added that a further 1,538 civilians had lost their lives in regions including Kyiv, Kharkiv in the east, Chernihiv in the north, and Kherson in the south.
The agency also said that 3,397 civilians had been injured since the Russian invasion began on February 24.
The agency said it believes the actual number of deaths and injuries to be significantly higher. It cited delays in receiving information and difficulty corroborating reports from areas under heavy bombardment by Russian forces, such as Mariupol.