Japanese Ambassador to Russia Akira Muto spent about 20 minutes at the Foreign Ministry building on Smolenskaya Square, where he was handed a 'resolute protest' over Tokyo's response to Vladimir Putin's trip to the Kuril Islands. The diplomat did not answer journalists' questions after the visit.

The Russian Foreign Ministry said Russia's sovereignty and jurisdiction over the southern Kuril Islands are 'unshakable' and called Japan's attempts to question them 'unacceptable and illegal.' The ministry also said Moscow reserves the right to take countermeasures in response to Tokyo's adherence to the sanctions policy of the 'collective West.'

Last week, Putin visited Iturup — one of the islands in the Kuril archipelago that is the subject of a territorial dispute between Russia and Japan — for the first time. Japanese Prime Minister Sanae Takaichi called the trip 'absolutely unacceptable' and 'hurtful to the feelings of the Japanese people,' and Japan's Foreign Ministry summoned Russian Ambassador Nikolai Nozdrev.

Earlier, Russian Foreign Minister Sergei Lavrov said Muto had failed to appear when summoned, with the embassy explaining that the diplomat was 'either not in Moscow or feeling unwell.' Lavrov also noted that Muto had recently brought a delegation of Japanese businesspeople to Russia without coordinating with the Russian Foreign Ministry.

Japan's government, according to NHK, is considering tightening sanctions against Russia in response to Putin's visit to Iturup.

Because of the territorial dispute, Moscow and Tokyo have yet to sign a peace treaty formally ending World War II hostilities.