EPAUkrainian forces have captured two Chinese nationals who were fighting for the Russian army in eastern Ukraine's Donetsk region, President Volodymyr Zelensky has said.
The Ukrainian president said intelligence suggested the number of Chinese soldiers in Russia's army is "much higher than two".
Ukraine's Foreign Minister Andrii Sybiha said that Chinese troops fighting on Ukrainian territory "puts into question China's declared stance for peace" and added that their envoy in Kyiv has been summoned for an explanation.
It marks the first official allegation that China is supplying Russia with manpower for its war in Ukraine. There has been no immediate response to the claims from Moscow or Beijing.
In a statement on social media platform X, Zelensky said the soldiers were captured in Ukraine's eastern Donetsk region with identification documents, including bank cards which had "personal data" on them.
Ukraine's forces fought six Chinese soldiers and took two of them prisoner, he said.
The post was accompanied by a video showing one of the alleged Chinese captives in handcuffs, speaking Mandarin Chinese and apparently describing a recent battle.
"We have information suggesting that there are many more Chinese citizens in the occupier's units than just these two," he said.
"Russia's involvement of China, along with other countries, whether directly or indirectly, in this war in Europe is a clear signal that Putin intends to do anything but end the war," he said.
Zelensky called for a response "from the United States, Europe, and all those around the world who want peace".
An investigation is under way and the captives are currently in the custody of Ukraine's security service, he added.
Ukraine's foreign minister said that he had summoned China's charge d'affaires in Kyiv to "demand an explanation".
Writing on X, Andrii Sybiha said: "We strongly condemn Russia's involvement of Chinese citizens in its war of aggression against Ukraine, as well as their participation in combat against Ukrainian forces."
He added that "Chinese citizens fighting as part of Russia's invasion army in Ukraine puts into question China's declared stance for peace and undermines Beijing's credibility as a responsible permanent member of the UN Security Council".
French newspaper Le Monde has previously reported that it identified around 40 accounts on TikTok's sister app, Douyin - which is only available in China - belonging to Chinese individuals who claim to have signed up with the Russian army.
North Korea has sent thousands of troops to aid Russia's war effort against Ukraine, according to Kyiv and Western officials.
In a press conference on Tuesday, Zelensky said: "North Koreans fought against us on the front in Kursk, the Chinese are fighting on the territory of Ukraine."
In January Ukraine said it captured two injured North Korean soldiers in Russia's Kursk Oblast.
While Beijing and Moscow are close political and economic allies, China has attempted to present itself as a neutral party in the conflict and has repeatedly denied supplying Russia with military equipment.
One of Russia's chief advantages in the war is numbers. There have been reports of Moscow using "meat grinder" tactics to throw huge numbers of soldiers at the front lines and incrementally improve their position.
Russian President Vladimir Putin launched a full-scale invasion of Ukraine in 2022, and Moscow currently controls about 20% of Ukraine's territory, mostly in the east.
