Ukrainian President Volodymyr Zelenskyy says he has intelligence indicating 155 Chinese citizens are fighting for Russia on his country's soil.
The claim comes a day after Mr Zelenskyy announced his military had captured two Chinese men fighting with a Russian unit in eastern Ukraine — information that has since been backed by a high-ranking US official.
While Beijing is yet to respond to Mr Zelenskyy's latest claims, a spokesperson for China's foreign ministry said earlier in the day the country was reviewing information about its citizens serving alongside Russian troops.
The spokesperson said China discouraged its citizens from travelling to war zones.
Russia and Ukraine both accept foreign fighters in their militaries.
Mr Zelenskyy's claim that 155 Chinese troops are fighting with Russia was made to reporters in Kyiv, and has not been independently verified.
On Wednesday, local time, Mr Zelenskyy claimed Russia was using social media to recruit Chinese citizens to fight in its army, and said Beijing was aware of this.
Russia, which launched its full-scale invasion of Ukraine more than three years ago, is yet to respond to the claims.
Earlier on Wednesday, Admiral Samuel Paparo, the head of US forces in the Indo-Pacific, confirmed Mr Zelenskyy's claim from the previous day that his army had captured two Chinese nationals.
"They did, and any success offensively in Europe will embolden the PRC and their own offensive ambitions," he told a congressional hearing in Washington DC.
Mr Zelenskyy said the men had been part of a group of six Chinese soldiers that his troops had fought against in his country's Donetsk region.
He didn't specify what happened to the other four.
Mr Zelenskyy said his country was ready to return the two Chinese prisoners of war, in exchange for Ukrainians soldiers who had been captured by Russia.
While Ukraine's president has used the incident as evidence that another country had entered the war, analysts have warned it's unlikely China would have supplied the troops to Russia in an official capacity — something that would be seen as a major escalation.
Last year, North Korea sent thousands of troops to fight with Russia.
Russia and China are allies, but Beijing has repeatedly denied sending military aid to Russia over the course of its full-scale invasion of Ukraine.
Although, it has been accused of supplying Russia with dual-use items, which can be used for military or civilian purposes.
This weeks revelations come amid flailing efforts, led by the US, to broker a ceasefire between Russia and Ukraine.
On Wednesday, the European Commission Vice-President Kaja Kallas said Russia's attacks on Ukraine had only increased since a proposal for a truce was put forward last month.
While Ukraine agreed to the plan, Russia did not.
Russian media outlets on Wednesday claimed the country's forces had struck a missile production facility in Ukraine.
