Zelensky -- whose war leadership has hit turbulence with Donald Trump in the White House -- also said that Kyiv was ready to buy up to $50 billion of US military equipment.

He said Ukrainian officials were due to hold a meeting with a US delegation next week as part of Washington's efforts to push Moscow and Kyiv to agree to a ceasefire.

Kyiv had details of more than 150 Chinese nationals who had deployed to the front, Zelensky said, a day after claiming Ukraine's army had captured two Chinese citizens fighting in the eastern Donetsk region.

Zelensky said Ukraine was ready to release the captured Chinese citizens in exchange for Ukrainian POWs held in Russia.

"Such an overt involvement of Chinese citizens in combat operations on the territory of Ukraine is a deliberate step towards expanding the war," Zelensky said. "This is yet another indication that Moscow simply needs to drag out the fighting."

The fresh criticism of both Russia and China came hours after Beijing rejected the idea that its citizens had been recruited in big numbers to fight with Russia, and warned Chinese nationals to "avoid involvement in armed conflicts".

"This is the second mistake for Russia. The first was North Korea. They drag other countries into war. I believe that they are now dragging China into this war," Zelensky told reporters in Kyiv.

According to Kyiv, South Korea and Western intelligence, Pyongyang last year despatched more than 10,000 of its soldiers to support Russia's army after Ukraine launched a brazen cross-border attack on the western Kursk region.

"The 'Chinese' issue is serious. There are 155 people with names and passport details who are fighting against Ukrainians on the territory of Ukraine," Zelensky told journalists in Kyiv.

A document shared with AFP by a senior Ukrainian official contained the alleged names and passport details of 168 Chinese citizens that Kyiv said had been recruited by Russia's army, according to its intelligence.

Zelensky said he believed there were "many more" and that further information was being gathered.

He did not accuse Beijing of having directly sent the soldiers, but said Chinese authorities were aware they were being recruited.

"It is clear how they recruit them. One of the schemes is through social media, in particular TikTok and other Chinese social networks, where Russians distribute commercials," Zelensky said.

"Beijing is aware of this," he added.

- 'Absolutely groundless' -

Zelensky had a day earlier published a video of one of two alleged captured Chinese citizens wearing military fatigues and with hands bound.

In the video, the prisoner mimicked combat sounds and uttered several words in Mandarin. The Ukrainian army said Chinese ID cards and contracts for Russian military service had been found on them.

Chinese foreign ministry spokesman Lin Jian had earlier rejected Zelensky's previous claim that "many" Chinese citizens had been recruited by Russia to fight as "absolutely groundless".

"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 about the captured Chinese citizens with Kyiv.

Asked about Zelensky's claims in a daily press briefing, Kremlin spokesman Dmitry Peskov declined to comment.

China presents itself as a neutral party in the three-year war 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 invasion, 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," he added.

- 'Unacceptable' -

Zelensky said he had received signals that Washington viewed Chinese nationals fighting for Russia as "unacceptable".

"The United States of America is very much surprised and believes that this is unacceptable. These are the signals they have sent us," he told reporters.

Addressing US-Ukrainian cooperation, Zelensky said Kyiv had indicated to Washington it wanted to buy a "large package" of defence materiel.

"We are ready to find 30 billion or 50 billion (dollars)" for US military equipment, he said.