President Volodymyr Zelenskiy said on Tuesday that Chinese citizens were working at a drone production site in Russia and suggested that Moscow may have "stolen" drone technology from China.
The Ukrainian leader made the comment at a news conference in Kyiv days after he said China was supplying weapons and gunpowder to Russia, the first time he has accused Beijing of direct military aid to Moscow, something China staunchly denies.
Ukraine's Foreign Ministry said it had summoned Chinese Ambassador Ma Shengkun and expressed Ukraine's "serious concerns" over Chinese involvement in Russia's war in Ukraine.
Zelenskiy, in suggesting that Russia may have obtained drone technology from China without Beijing actually knowing, appeared to be softening his tone towards China, which casts itself as neutral on the war.
The flurry of Ukrainian allegations directed at China, the world's second largest economy, in recent days has been particularly striking at a sensitive moment for Kyiv in the US-led diplomatic effort to end the war.
Zelenskiy said earlier this month that Russia was recruiting Chinese nationals via social media to fight in its armed forces and that Beijing officials were aware of that. He added that Kyiv was trying to assess whether the recruits were receiving instructions from Beijing.
China has reaffirmed its support for peace efforts in Ukraine and said relevant parties should avoid "irresponsible remarks," in an apparent jab at Zelenskiy's comment about Chinese citizens fighting there for Russia.
Zelenskiy told reporters on Tuesday that he had instructed officials to send information to the Chinese government through official channels on its findings.
"Separately, I asked the Security Service of Ukraine to transfer information of a broader nature to the Chinese side regarding Chinese citizens who work at the drone factory," he said.
"We believe that it may be that Russia stole - made an agreement with these citizens outside the agreements with the Chinese leadership - stole these technologies."
A Foreign Ministry statement said Ukraine expressed "serious concerns about the facts of the participation of Chinese citizens in military action against Ukraine on the side of the aggressor-state and also the involvement of Chinese companies in the manufacture in Russia of military goods."
It said Deputy Foreign Minister Yevhen Perebyinis "called on the Chinese side to take measures to stop supporting Russia in its aggression against Ukraine, the absence of which has been repeatedly stated by Beijing".
China's foreign ministry on Wednesday reiterated that China is firmly opposed to "groundless accusations and political manipulation" when asked about the latest Ukrainian claims.
There was no immediate comment on any of the Ukrainian statements from Russia.
China and Russia declared a "no limits" strategic partnership days before Russian President Vladimir Putin sent tens of thousands of troops into Ukraine in February 2022.
