Ukraine said on Monday that North Korean units fighting for Russia sustained losses of at least 30 soldiers killed or wounded around several villages on the front in Russia's Kursk region over the weekend.
The Ukrainian military spy agency's statement came after President Volodymyr Zelenskiy said on Saturday that Russia was using North Korean troops in significant numbers for the first time to conduct assaults in Kursk, a Russian region where Ukraine launched a cross-border incursion in August.
The statement is the first time Kyiv has claimed North Korean losses on this scale and in some detail. It said the casualties occurred around the villages of Plekhovo, Vorozhba and Martynovka in the Kursk region. It provided no evidence.
It was not possible to independently verify the figures.
The Kremlin declined to comment on the Ukrainian assertion, referring the question to the Russian Defense Ministry which has made no comment on the subject.
Russia has neither confirmed nor denied the presence of North Koreans on its side. Pyongyang initially dismissed reports about the troop deployment as "fake news", but a North Korean official has said any such deployment would be lawful.
"Due to the losses, the assault groups are being replenished with fresh personnel, in particular from the 94th separate brigade of the DPRK army, to continue active combat operations in Kursk region," the Ukrainian agency wrote.
Kyiv first said North Korean forces turned up in Russia's Kursk region in October and later reported unspecified clashes and casualties. It estimates there are 11,000 North Koreans in total, adding to a force of tens of thousands of Russians.
Ukraine, nearly a fifth of which is controlled by Moscow's forces, has carved out an enclave in the Kursk region which its troops have been battling to hold as a potential bargaining chip for any potential peace negotiations.