Japan said it "strongly protests" Russian President Vladimir Putin's visit to a disputed island in the Pacific.

Russian state media reported on Thursday that Putin visited Iturup – known in Japan as Etorofu – one of four islands in the Kuril chain that are claimed by both Russia and Japan.

Japan's foreign minister Toshimitsu Motegi said the islands are "inherently Japanese territory both historically and under international law, and the Government of Japan strongly protests this visit".

The two countries have been locked in a dispute over the Kuril islands for decades.

This dispute was the main reason Moscow and Tokyo did not sign a peace treaty after World War Two.