As many as 31,000 Ukrainian soldiers had been killed since Russia's full-scale invasion two years ago, Volodymyr Zelensky said Sunday (Feb 25), giving the first official figure for more than a year.

He told a news conference in Kyiv that he could not disclose the number of wounded because it would help Russian military planning.

He said: "31,000 Ukrainian troops have been killed in this war. Not 300,000, not 150,000 ... (Russian President Vladimir) Putin is lying there ... But nevertheless, this is a big loss for us."

Ukraine has not put a number to its military losses since the end of 2022, when presidential aide Mykhailo Podolyak said 13,000 Ukrainian soldiers had been killed since the invasion on February 24.

Battlefield casualties are a highly sensitive subject in a country trying to reform how it mobilises civilians into the army to regenerate its forces after last year's counteroffensive proved unable to break through Russian lines.

A New York Times report in August cited US officials as putting the Ukrainian death toll at close to 70,000. The same report said as many as 120,000 Russian troops had died during the war.

Zelenskiy told reporters that 180,000 Russians had been killed in the fighting.

Russia does not disclose military losses, which it regards as secret. Both sides regularly describe the other's military losses as vast.

The Ukrainian leader also said that tens of thousands of civilians had been killed in the occupied areas of the country during the war. Kyiv says it cannot accurately assess the scale of such losses because it does not have access.