Russian President Vladimir Putin made his first-ever visit to the disputed Kuril Islands on Thursday, touring a fish-processing plant, a hospital and a school on the southernmost isle of Iturup and meeting with the regional governor, according to the Washington Post.

Japanese Prime Minister Sanae Takaichi immediately condemned the trip, calling it "absolutely unacceptable" and saying it "wounds the feelings" of the Japanese people, per Al Jazeera. Japan's Foreign Minister Toshimitsu Motegi went further, summoning Russia's ambassador to lodge a formal protest and insisting the islands "are an inherent part of Japan's territory both historically and under international law."

ABSOLUTELY UNACCEPTABLE.

A dispute that outlasted the Soviet Union

Known in Japan as the Northern Territories and in Russia as the Southern Kurils, the islands were seized by Soviet forces in the final days of World War II and have remained a source of diplomatic friction between Moscow and Tokyo for eight decades — the two countries have technically never signed a peace treaty formally ending their WWII hostilities because of the standoff.

Relations soured further after Russia's 2022 invasion of Ukraine, when Japan joined Western allies in imposing sanctions on Russian officials and entities. Putin's decision to personally visit the islands for the first time in his more than two decades in power is widely read as a deliberate signal that Moscow has no intention of ever returning the territory, even as it seeks to project strength on multiple fronts.

Russian state media framed the trip around economic development on Iturup, with Putin inspecting local infrastructure and business investment, according to the Irish Times. Japanese officials, however, framed it purely as a provocation.

What's next

Tokyo is expected to raise the visit at upcoming diplomatic forums and press allies for a coordinated response, though Japan's options for retaliation remain limited given already-extensive sanctions on Moscow. Analysts say the episode is likely to further chill any prospect of renewed Russia-Japan territorial talks for the foreseeable future.