Kyiv, Ukraine - Ukrainian President Volodymyr Zelensky on Sunday said 31,000 soldiers defending the country from Russia's invasion have been killed, in what is the country's first official figure for military casualties in more than two years of fighting.

"I don't want to mention the number of wounded," Zelensky said at a press conference.

US and Russian officials had previously said between 100,000 and 300,000 Ukrainian soldiers had been killed in the conflict, figures which Zelensky dismissed as "nonsense."

The Ukrainian leader meanwhile put Russian losses at 180,000 dead and 500,000 wounded.

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This is the first time that one of the warring parties has released its own official casualty figures. The veracity of the toll cannot be officially verified.

The Russian casualty figures cited by Zelensky are significantly higher than the daily updated toll by the Ukrainian armed forces, which on Sunday put the total number of Russian losses at 409,820 dead and wounded combined.

Zelensky declined to comment on the casualties among the Ukrainian population and said such figures are not currently known. The Office of the UN High Commissioner for Human Rights has previously put forward a conservative estimate of 10,000.

Exact casualties among military personnel have so far been kept strictly secret by both sides. US estimates from mid-2023 put the number of Ukrainian soldiers killed at around 70,000 and the number of Russian soldiers killed at 120,000.

In mid-February, the US Department of Defense estimated the number of Russian soldiers killed or wounded at 315,000.