Russia delivered a strong protest to Japan's ambassador to Moscow on Tuesday over what it called anti-Russian remarks by Prime Minister Sanae Takaichi in a dispute over a group of Russian-controlled islands off northeast Japan.
Moscow's summoning of envoy Akira Muto is the latest development in a simmering row between the two countries after Russian President Vladimir Putin visited one of the disputed islands last week.
The four islands, which Russia calls the Southern Kurils and Japan refers to as the Northern Territories, were seized by the Soviet Union in the days following Japan's surrender in World War Two.
Russia controls and administers them, but Tokyo still claims them. Takaichi said last week that Putin's visit "hurts the feelings of the Japanese people and is absolutely unacceptable".
Deputy Foreign Minister Mikhail Galuzin delivered Moscow's protest to the Japanese envoy, telling him Moscow objected to "anti-Russian" statements by both Takaichi and Foreign Minister Toshimitsu Motegi.
"The Russian side stated that Russia’s sovereignty and jurisdiction over the Southern Kuril Islands are indisputable," the ministry said in a statement after the meeting.
It said the islands legally belonged to Russia, adding: "Any attempts by the Japanese side to directly or indirectly call this obvious reality into question are absolutely unacceptable and unlawful."
The island dispute, unresolved for eight decades, has prevented Russia and Japan from concluding a formal peace treaty that would unlock closer economic ties between them.
Relations have worsened sharply since Russia launched a full-scale war against Ukraine in 2022 and Japan joined other nations in condemning it and imposing sanctions against Russia.
In light of Japan's participation in the sanctions and its support for Ukraine, Muto was told that Moscow reserves the right to take "appropriate countermeasures", the Russian statement said, without elaborating.
The envoy left the foreign ministry without commenting to reporters.
