Russian President Vladimir Putin on Thursday made his first visit to the Kuril Islands, a Moscow-controlled Pacific archipelago that also is claimed by Japan, which voiced a diplomatic protest over the trip.

Russian President Vladimir Putin on Thursday visited the Moscow-controlled Kuril Islands claimed by Japan for the first time, travelling to Iturup in a move that prompted a strong diplomatic protest from Tokyo.

Putin toured a fish-processing facility, a hospital and a school on the volcanic island and also met local residents and the governor of Russia’s Sakhalin region, Valery Limarenko.

Japan claims the four southernmost islands of the Kuril chain, which it calls the Northern Territories. The Soviet Union took control of the islands in the final days of World War II, and the territorial issue has remained a major obstacle to Moscow and Tokyo signing a formal peace treaty.

Japan summons Russian ambassador

Japanese Foreign Minister Toshimitsu Motegi strongly protested Putin’s visit to Iturup, known as Etorofu in Japan.

“The Northern Territories, including Etorofu (Iturup) Island, are Japan’s inherent territory both historically and from the perspective of international law,” Motegi said.

Tokyo summoned Russian Ambassador Nikolay Nozdrev to the Foreign Ministry and demanded that he convey Japan’s protest to Moscow.

Japan’s Prime Minister Sanae Takaichi called the visit “absolutely unacceptable” and said it was incompatible with Tokyo’s position on the Northern Territories.

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She warned that the trip would further damage already strained relations between the two countries, particularly following Japan’s support for sanctions against Russia after its invasion of Ukraine.

Moscow rejects Japan’s territorial claim

Russia dismissed Tokyo’s objection as unfounded, with its embassy saying the southern Kuril Islands are an integral part of the Russian Federation and became Russian territory following World War II.

The Russian side also argued that Putin’s visit was a sovereign decision that did not require consultation with other countries.

Putin had visited Russia’s Far East in recent days and travelled to Sakhalin before heading to Iturup. He also observed exercises involving Russia’s Pacific Fleet.

Speaking aboard a warship taking part in the drills, Putin defended Moscow’s position on the islands, saying their current status was established through international documents following World War II.

At the same time, he said Russia remained open to negotiations aimed at reaching a peace treaty with Japan, recalling his past efforts to improve ties with former Japanese Prime Minister Shinzo Abe.

Putin blamed the deterioration in relations partly on Japan’s decision to impose sanctions on Russia and designate Moscow as a primary security threat.

Kuril dispute deepens Russia-Japan tensions

Japan has continued limited engagement with Russia partly to facilitate visits by former Japanese residents to the islands, including trips to pay respects at family graves.

But Putin’s visit risks making those efforts more difficult.

Former Russian president Dmitry Medvedev, now deputy chairman of Russia’s Security Council, rejected Takaichi’s criticism, declaring on X that the Kuril Islands “were, are, and will remain Russian land.”

He added a warning that those who failed to accept that reality would face what he called the “monstrous consequences” of their mistake.

With inputs from agencies