Ukraine's top military commander, Oleksandr Syrskyi, reportedly said that his country has numerous reports of North Korean soldiers preparing to participate in combat operations alongside Russian forces.

Reuters said on Sunday that Syrskyi made the remarks in a Facebook post on Saturday.

In the post, Syrskyi wrote that he told General Christopher Cavoli, who heads the United States European Command, that the situation remains "challenging" and shows "signs of escalation."

Ukrainian and U.S. authorities earlier said that there was a "small-scale" engagement between North Korean soldiers and Ukrainian troops last Monday.

On Thursday, media reports said that North Koreans fought together with Russia's 810 Naval Infantry Brigade in Russia's Kursk region.

On the same day, President Volodymyr Zelenskiy said that some of the eleven-thousand North Korean troops deployed to the Kursk region had taken part in fighting and had suffered casualties in combat with Ukrainian forces.