Japan said it “strongly protests” Russian President Vladimir Putin’s visit to a disputed island chain.
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.
The Kuril islands sit between Hokkaido in northern Japan and Russia’s Kamchatka Peninsula. Four of the southernmost islands are claimed by Japan, which calls them the Northern Territories.
They are administered by Russia. At the end of World War Two, the Soviet Union annexed the island chain and deported around 17,000 Japanese residents.
During his visit on Thursday, Putin sampled fish roe and spoke to island locals, Russian state media reported.
The islands are strategic spots for Russia’s military operations, with Iturup being used as its primary military air base in the region.
Last month, Chinese and Russian naval warships sailed through a strait in the Kuril islands during a joint patrol.
Russia also held military drills near the islands last year, drawing condemnation from Japan.
