"The formula for the successful implementation of China's 'Peace Plan'. The first and foremost point is the surrender or withdrawal of Russian occupation forces from (Ukrainian territory) in accordance with international law and the UN Charter," the secretary of Ukraine's National Security and Defence Council, Oleksiy Danilov, wrote on Twitter.

The call comes as the Chinese and Russian leaders applauded on Monday the solidity of their alliance as the Chinese leader headed to Moscow for a summit with the internationally isolated Russian president.

Xi described his trip as a "journey of friendship, cooperation and peace", though China has been criticised by Western nations for what they consider tacit backing and diplomatic cover for Russia's war in Ukraine.

"I look forward to working with President Putin to jointly adopt a new vision" for relations, Xi wrote in a signed article in the newspaper Russian Gazette that was also carried by Chinese state news agency Xinhua.

China has sought to portray itself as a neutral party in the Ukraine war, and its foreign ministry said last week that Beijing would "play a constructive role in promoting peace talks" between Kyiv and Moscow.

Beijing in February issued a 12-point position paper calling for dialogue and respect for all countries' territorial sovereignty.

Putin has welcomed Beijing's statements on Ukraine as being indicative of a willingness to play a "constructive role" in ending the conflict, while saying Chinese-Russian relations were "at the highest point".