MOSCOW - Russia's security agency said Tuesday it has detained a Japanese journalist with the Sapporo-based Hokkaido Shimbun newspaper on Sakhalin in the Russian Far East on suspicion of spying.

The male reporter, posted at the newspaper's bureau in Yuzhno-Sakhalinsk on the Russian island, was allegedly working for a Japanese intelligence service and collecting information related to Russia's defense capabilities, according to Tass news agency.

Citing Russia's principal security agency, the FSB, Tass said he was placed in custody after being transported to Moscow, while the agency's Investigative Directorate has opened a criminal case against him. Russian media said a Moscow court had approved his detention for two months.

Espionage carries a prison sentence of 10 to 20 years.

Resolution of the case could take some time, given that Russian authorities have remanded the journalist rather than deporting him.

The episode casts a further cloud over bilateral relations that have deteriorated since Moscow launched a full-scale invasion of Ukraine in 2022, prompting Japan to impose economic sanctions on Russia.

The Russian Foreign Ministry said the journalist was detained Tuesday. It accused Japan of using its correspondents to gather information for the purpose of undermining Russia's national security, calling the attempt "regrettable."

According to Tass, the ministry called on Tokyo to stop hostile actions against Moscow, saying bilateral ties have deteriorated, partly because of Japan's "anti-Russian course."

The ministry also referred to Japan's unwillingness to heed Moscow's concerns about what it calls the Asian nation's "remilitarization," which it said affects Russia's legitimate security interests in the Russian Far East, the report said.

An official at the Japanese Embassy in Moscow as well as the newspaper told Kyodo News that they are trying to confirm the details of the report.

The FSB said the reporter allegedly gathered information on mobilized and volunteer soldiers from the Kuril Islands involved in what Russia calls its special military operation in Ukraine.

The Kurils are a chain of islands stretching between Russia's Kamchatka Peninsula and Japan's northern main island of Hokkaido. Japan claims four of the islands nearest Hokkaido, calling them the Northern Territories. Russia has controlled them since Soviet forces occupied them after Japan's surrender in World War II in 1945.

The Hokkaido Shimbun daily is the only Japanese media outlet with a permanent Japanese correspondent on Sakhalin and is known for extensive reporting on the Russian Far East as well as the disputed islands.

On Oct. 2, the Japanese government announced additional sanctions against Russia in connection with its invasion of Ukraine, targeting a so-called shadow fleet of vessels engaged in transporting sanctioned oil from Russia.

Japan, in lockstep with the other Group of Seven members, has imposed economic sanctions on Russia, including freezing the assets of Russian President Vladimir Putin and other individuals.