Moscow said Monday it had summoned the Japanese ambassador after Tokyo condemned President Vladimir Putin's recent visit to Russia's far-eastern Kuril Islands, which are also claimed by Japan.

Russian-Japanese relations have long been dogged by the contested islands, known in Japan as the Northern Territories and seized by the Soviet Union in 1945.

Putin, 73, travelled to the islands after visiting the nearby Russian island of Sakhalin, prompting Japan to summon Russia's ambassador in protest.

Moscow retaliated by summoning Japanese envoy Akira Muto.

Japanese officials had "crossed the line of decency" in criticising Putin's trip, Foreign Minister Sergei Lavrov said Monday.

"We have summoned the (Japanese) ambassador," Lavrov told reporters, adding that Tokyo had initially said Muto could not attend immediately.

"We were told either that he was not in Moscow or that he was unwell. We did not quite understand the situation," Lavrov said.

Ministry spokeswoman Maria Zakharova later told state news agency TASS that after Lavrov's comments the ambassador had "suddenly started feeling better" and would attend on Tuesday.

Lavrov said Muto's summons was intended to address "the conduct of the Japanese leadership" and how ambassadors "should conduct themselves in the host country".

Ties between Japan and Russia have worsened since the full-scale conflict in Ukraine began in 2022.

Japan has joined other G7 countries in sanctioning Russia and giving money and non-lethal defence aid to Kyiv.