China has presented itself as a neutral party since Russia invaded Ukraine in 2022, although Kyiv's allies have long accused Beijing of secretly helping its close partner Moscow.

EU foreign affairs chief Kaja Kallas said on Monday the bloc had now "verified reports that the Chinese military has been training Russian military personnel to fight in Ukraine", calling Beijing a "decisive enabler" of the war.

Asked about the comments at a regular news briefing, a spokesman for China's foreign ministry said: "The relevant claims have no factual basis. It is pure slander and smearing."

Several media outlets reported last month that European intelligence agencies believed China had conducted the training.

A senior EU official confirmed the reports on Friday, saying the training was happening in several locations in China and that "hundreds" of troops were involved.

Kallas said on Monday the EU had sanctioned several Chinese entities in response.

The allegations bolster suspicions that Beijing has offered more material support to Moscow than publicly disclosed.

Ties between China and Russia have strengthened since the war began, with Beijing providing an economic lifeline to diplomatically isolated Moscow.