Moscow said Wednesday it was expelling eight Japanese diplomats in a tit-for-tat response to expulsions by Tokyo over the conflict in Ukraine.

Accusing Tokyo of pursuing an "openly hostile anti-Russian course," the foreign ministry said in a statement that the Japanese diplomats must leave by May 10, in a reciprocal answer to Japan's expulsion of eight Russian diplomats.

It accused Tokyo of "taking steps that were unprecedented in modern Russian-Japanese relations" and "abandoning friendly, constructive relations with Russia".

Earlier this month Japan expelled the eight Moscow diplomats and announced it will end imports of Russian coal over the military campaign in Ukraine.

Japan has marched in lockstep with Western allies on sanctions against Russia since the start of the conflict on February 24. 

Tokyo has complex relations with Moscow, with attempts to sign a post-World War II peace treaty hampered by a long-running dispute over islands that Japan says are "illegally occupied" by Russia. 

Russia and the West have imposed a series of tit-for-tat measures over the conflict, including diplomatic expulsions and travel bans.