Russia's top diplomat Sergei Lavrov was visiting Beijing after a trip to North Korea, where he received assurances of support for Moscow's invasion of Ukraine.

Wang told Lavrov on Sunday that "China-Russia are the most stable, most mature and most strategically valuable relationship between major powers in the world today", according to a Chinese foreign ministry readout of their meeting.

"The current focus is to... deepen comprehensive strategic cooperation, promote each side's development and revitalisation, and jointly respond to the challenges brought by a turbulent and changing world," Wang said.

The two ministers "exchanged views on the Korean peninsula, the Ukraine crisis, the Iranian nuclear issue and other matters", the Chinese statement said.

It did not mention ties with Washington, which Moscow said was also on the agenda.

The Russian foreign ministry said Lavrov and Wang also discussed other "burning issues", including the war in Gaza.

China, a diplomatic and economic ally of Moscow, claims to be neutral in the conflict between Russia and Ukraine.

However, it has never denounced Russia's 2022 invasion nor called for it to withdraw its troops, and many of Ukraine's allies believe that China has provided support for Russia.

Beijing regularly calls for an end to the fighting, while also accusing Western countries of prolonging the conflict by arming Ukraine.