The Chinese People's Liberation Army (PLA) reportedly hosted covert training for several hundred Russian soldiers late last year at six military bases in China, the newspaper reported on Wednesday, citing the classified documents.

The training, according to the report, focused primarily on the deployment of drones and electronic countermeasures, with many of the Russians sent to fight in Ukraine soon after, including with Russia's elite "Rubicon" frontline drone unit.

AFP could not independently verify the newspaper report.

China has claimed neutrality in the ongoing Russian invasion of Ukraine, but the Die Welt report would bolster suspicions that Beijing has offered more support to its Russian allies than publicly disclosed.

Chinese troops have also reportedly received secret training in Russia.

Die Welt reported that European intelligence sources believe that roughly 600 PLA soldiers spent time at Russian military bases last year learning about armoured combat, artillery deployment and air defences.

European intelligence agencies also believe that Russia and China have been sharing extensive information about advanced European and US-made weapons used by Ukraine, including equipment captured on the battlefield by Russian troops.

- 'Increasingly close cooperation' -

According to the Die Welt report, particular interest has focused on US-made HIMARS rocket launchers, Patriot air-defence systems, German-made Marder armoured vehicles, and American Abrams main battle tanks.

China has faced criticism from Western countries over extensive exports to Russia of so-called dual-use goods, products like semiconductors and small electric motors that are used in both military weaponry and civilian products.

Chinese President Xi Jinping welcomed Russia's Vladimir Putin in Beijing on Tuesday for a visit.

Ties between China and Russia have stengthened in the years since Putin launched the full-scale invasion of Ukraine in 2022, with Beijing refusing to condemn Moscow's war.

Putin has also become more reliant on China, as Western sanctions have squeezed oil revenues and made China the dominant buyer of Russian oil.

Xi told Putin on Wednesday that their two countries have "continuously deepened our political mutual trust and strategic coordination with a resilience that remains unyielding", according to Chinese state media.

Marc Henrichmann, the chairman of the German parliament's intelligence oversight committee, said he considered the Die Welt report plausible, saying it "aligns with the developments we have observed in recent years".

"Particularly since the beginning of Russia's war of aggression, increasingly close cooperation between Moscow and Beijing has become apparent in both the military and economic spheres," he told the Handelsblatt newspaper.

"Since 2022, a large part of the Russian war machine has been powered by Chinese dual-use components, from fibre optic cables for drones and chips to engines and propulsion systems for long-range weapons," he said.