Britain's defense ministry says up to 250,000 Russian troops have died since Russian forces invaded Ukraine in 2022.

The ministry posted on social media on Thursday that Russian forces have likely sustained about 900,000 casualties, and 200,000 to 250,000 of these have been killed. It says the deaths are Russia's largest losses since the World War Two.

The ministry says Russian President Vladimir Putin and the Russian military leadership are almost certainly prepared to tolerate high casualty rates so long as this does not negatively affect public or elite support for the war, and those losses can be replaced.

It also says Putin and the leadership highly likely place significantly less value on the lives of ethnic minority Russian citizens from impoverished regions, where military recruitment efforts have been focused.

It adds that Slavic Russians from urban centers such as Moscow have contributed disproportionately fewer service personnel than poorer, ethnic minorities.