Russia has turned increasingly to China as its most powerful ally since alienating the West last year with its decision to launch a full-scale invasion of Ukraine, what it calls a "special military operation".

China has declined to blame Moscow for the war and condemned Western sanctions on Russia, even as it has profited by securing discounts for oil and gas that Russia can no longer sell to Europe.

Kremlin foreign policy adviser Yury Ushakov said in July that Putin planned to visit China in October at the time of its third "Belt and Road" forum, responding to an invitation issued by Xi during a high-profile state visit to Russia in March.

Putin and Xi had already heralded an era of much closer ties, and a shared rejection of a Western-based world order, by signing a "no limits" partnership agreement in Beijing last year, weeks before Russia invaded Ukraine.

But Putin, speaking in a televised meeting with selected schoolchildren on the first day of the school year, did not explicitly confirm that he would travel to China again.

Putin is not known to have travelled abroad since the International Criminal Court issued an arrest warrant for him in March, just before Xi's visit, on suspicion of war crimes in Ukraine.

"Quite soon we will have events, and there will be a meeting with the president of the People’s Republic of China," he said, according to Russian news agency Interfax.

"He (Xi) calls me his friend, and I am happy to call him my friend, because he is a person who does a lot for the development of Russian-Chinese relations."

Last week, Putin participated remotely in a summit of the BRICS countries, with Brazil, India, China and the host, South Africa.

He will be represented by Foreign Minister Sergei Lavrov at a Sept. 9-10 meeting of the Group of 20 leading industrialised and developing countries in India.