Zelensky said Tuesday that Kyiv had captured two Chinese citizens fighting alongside Russian forces, and that there was evidence "many more Chinese citizens" were fighting with Moscow.

Chinese foreign ministry spokesman Lin Jian told a press conference it was "absolutely groundless" to suggest many Chinese citizens were fighting in Ukraine.

"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," he said.

He added that Beijing was verifying relevant information with Kyiv.

The Kremlin declined to comment on the matter.

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 partner of Russia, and NATO members have branded Beijing a "decisive enabler" of Moscow's offensive, which it has never condemned.

"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," Lin said.

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

At least two people were killed and two wounded in Ukraine's eastern Donetsk region on Wednesday and one man died in the southern region of Kherson during Russian shelling, officials said, as the war grinds through its fourth year.

- Paid to join? -

Ukrainian troops had captured the two Chinese citizens fighting with Russian forces in the Donetsk region, Zelensky told reporters on Tuesday.

The media outlet Ukrainska Pravda, citing the Ukrainian army, reported that one of the captives had paid $3,480 to an intermediary in China to join the Russian army because he wanted to receive Russian citizenship.

The captive, who is now cooperating with the Ukrainian authorities, also said he was trained in the Russian-occupied Lugansk region as part of a group of Chinese nationals, some of whom had legal issues back home, according to Ukrainska Pravda.

Kyiv released a video of one 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 that there might be more of them.

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