"The Chinese side is verifying relevant information with the Ukrainian side," foreign ministry spokesman Lin Jian said.

"The Chinese government has always asked its citizens to stay away from areas of armed conflict (and) avoid involvement in armed conflicts in any form."

Zelensky told reporters including AFP on Tuesday that Ukrainian troops had captured the two Chinese citizens fighting with Russian forces in the Donetsk region of Ukraine.

Kyiv also released a post that included a video of the alleged Chinese prisoners showing a man wearing military fatigues with his hands bound.

He mimicked sounds from combat and uttered several words in Mandarin during an apparent interview with a Ukrainian official not pictured.

A senior Ukrainian official told AFP they were captured "a few days ago", adding there may be more of them.

They said the prisoners were likely Chinese citizens who were enticed into signing a contract with the Russian army, rather than being sent by Beijing.

The Kremlin declined to comment on the allegations.

"I have no way of commenting on this issue," Kremlin spokesman Dmitry Peskov told reporters, including journalists from AFP, on Wednesday.

Zelensky had said there was evidence that "many more Chinese citizens" were fighting with Russian forces, a claim Lin said was "absolutely groundless".

"The Chinese side's position on the issue of the Ukraine crisis is clear and unequivocal, and has won widespread approval from the international community," he said.

"The Ukrainian side should correctly view China's efforts and constructive role in pushing for a political resolution to the Ukraine crisis."

China presents itself as a neutral party in the conflict and says it is not sending lethal assistance to either side, unlike the United States and other Western nations.

But it is a close political and economic ally of Russia and NATO members have branded Beijing a "decisive enabler" of Moscow's offensive, which it has never condemned.