Xi, whom Putin calls a "dear friend", is the highest profile guest for Moscow's celebrations to mark the defeat of the Nazis. Russia has become increasingly economically reliant on China during its Ukraine offensive.

Beijing has portrayed itself as a neutral party throughout the conflict, but the West accuses it of enabling Russia economically and diplomatically.

"In the face of the international counter-current of unilateralism and hegemonic bullying behaviour, China will work with Russia to shoulder the special responsibilities of major world powers," Xi told Putin, hailing strengthening ties with Moscow.

"The political mutual trust between China and Russia is becoming deeper, and the ties for pragmatic cooperation are becoming stronger," he said.

Putin said Russia and China were "developing our ties for the benefit of the peoples of both countries and are not opposed to anyone."

Xi was in Moscow as Ukraine accused Russia of violating its own ceasefire within hours.

His visit comes ahead of large May 9 celebrations to mark 80 years since the defeat of Nazi Germany.

Putin said Russia and China will not forget the "27 million lives that the Soviet Union lay on the altar of the fatherland and the altar of victory, and the 37 million lives that the war took away from China for its freedom and independence."

Both countries defend "historical truth", said Putin, who has long accused the West of downplaying Moscow's part in WWII and argued the Soviet Union was the main victor in the conflict.

"Together with our Chinese friends we firmly stand on guard of historical truth, protect the memory of events of the war years and counter modern manifestations of neo-Nazism and militarism," Putin said.

Russian society has seen unprecedented militarisation during three years of conflict with Ukraine.