Russia's Federal Security Service said it arrested a Japanese newspaper reporter on Sakhalin Island on espionage charges, accusing him of gathering intelligence on Russian soldiers for Tokyo — a case that has reopened one of Asia's oldest and rawest territorial disputes.

The FSB told Russian state news agency TASS that a male correspondent for the Hokkaido Shimbun, a daily newspaper based in Japan's northernmost prefecture, was detained on Oct. 13 at a hotel in Yuzhno-Sakhalinsk, the Sakhalin regional capital, just hours before he was scheduled to fly home. State broadcaster Rossiya 24 cited investigators accusing him of compiling records on mobilized and contract soldiers recruited from the disputed Kuril Islands — known in Japan as the Northern Territories — who were sent to fight in Ukraine, and of intending to pass that material to Japanese intelligence. Al Jazeera reported the reporter was identified as Yuki Imai.

Two Months in Custody

A Moscow court approved two months of pretrial detention, and he was being moved from Sakhalin to the capital for further investigation, according to the Hokkaido Shimbun's own reporting on the case. A trial was expected to open around Dec. 12, Interfax reported. The reporter had been working in Russia on a valid journalist visa and had been reporting from Sakhalin and elsewhere in the country, the newspaper said.

Tokyo moved quickly. Foreign Minister Toshimitsu Motegi told a House of Representatives budget committee that Japan would work to protect its national, while Chief Cabinet Secretary Minoru Kihara said the embassy had so far been unable to contact the detained reporter. The Foreign Ministry summoned Russia's ambassador to Japan, Nikolay Nozdrev, on the evening of Oct. 14 to demand prompt information and humane treatment.

RUSSIAN FOREIGN MINISTRY SPOKESPERSON MARIA ZAKHAROVA CALLED TOKYO'S USE OF ACCREDITED CORRESPONDENTS TO GATHER INFORMATION "REGRETTABLE," SAYING THE CASE WAS NOT ISOLATED.

The arrest lands on top of a dispute that has simmered since the 1855 Treaty of Shimoda and hardened after the Soviet Union seized the southern Kuril Islands at the end of World War II — a seizure Japan has never recognized. The two countries still have no formal peace treaty. Tensions flared again in August, when President Vladimir Putin visited Iturup Island, prompting Prime Minister Sanae Takaichi to call the trip "absolutely unacceptable." Japan has since tightened sanctions on Moscow over the war in Ukraine, and Russia has labeled Japan an "unfriendly" country in response.

The Japan Foreign Correspondents' Club said it held "extremely strong concern" over the detention and pressed Russia to disclose its reasoning, while the Hokkaido Shimbun and the Japan Newspaper Workers Union called for the reporter's safety and swift release. The newspaper said confirming his condition was now its top priority.