Russian authorities have arrested a Japanese journalist on suspicion of espionage, accusing him of gathering information related to Moscow's defence capabilities for Tokyo.
The journalist, identified as Yuki Imai from the Hokkaido Shimbun newspaper, was detained in far eastern Sakhalin region, a day before he was due to leave Russia. He was flown to Moscow where a court ordered he be placed in pre-trial detention, Russian reports say.
Japan says it is still seeking details about the arrest, and has not been able to contact him.
The arrest comes as tensions worsen between the two nations after Russian leader Vladimir Putin visited the disputed Kuril Islands, claimed by both countries, in August.
Russian authorities allege that Imai "acted on the instructions of [Japan's] national intelligence service" to gather information about people involved in a special military operation on the Kuril Islands, state news agency TASS reported.
The Kuril islands sit between Hokkaido in northern Japan and Russia's Kamchatka Peninsula. The archipelago is administered by Russia, but four of the southernmost islands are claimed by Japan, which calls them the Northern Territories.
Imai has been taken to Moscow and will be remanded until 12 December, before his trial begins, according to Interfax, another Russian news agency.
Those convicted of espionage in Russia can be sentenced to up to 20 years in prison.
"Tokyo's attempts to use its correspondents in Russia, who hold foreign journalist status, to gather information aimed at undermining our country's security are regrettable," Russian foreign ministry spokeswoman Maria Zakharova said in a statement on Tuesday.
"We cannot help but point out that today's incident is not an isolated one," she noted, but did not name other journalists or media outlets that are allegedly involved in similar activity.
Imai's published work has covered Russia's relations with North Korea and life in Sakhalin.
Hokkaido Shimbun ran a report on the arrest without naming the reporter. "We are still confirming the details. Ensuring the reporter's safety is our top priority," it said in response to the BBC's queries.
Russia and Japan have been locked in a dispute over the Kurils for decades, and it is the main reason Moscow and Tokyo did not sign a peace treaty after World War Two.
Japan's Prime Minister Sanae Takaichi sharply criticised Putin's visit â his first-ever to the islands â saying it "wounded the feelings of the Japanese people" and is "incompatible with Japan's consistent position on the Northern Territories".
Moscow dismissed her remarks as "politically inappropriate" and "legally unfounded".
Over the years, attempts to resolve the territorial dispute have made little progress. Bilateral ties have also remained frosty, with Japan imposing sanctions against Russia for its invasion of Ukraine in 2022.
Last week, Moscow again angered Tokyo by requesting the extradition of the president of the International Criminal Court (ICC), who is Japanese.
The president Tomoko Akane, along with other ICC officials, has been placed on Russia's wanted list since 2023 after the court issued an arrest warrant for Putin over war crimes in Ukraine.
In 2023, Russia detained The Wall Street Journal's Evan Gershkovich on espionage charges and later sentenced him to 16 years in prison.
Gershkovich, a US citizen, was released in a 2024 prisoner swap, the largest exchange since the Cold War ended in 1991.
In 2019, Moscow detained an unnamed Japanese journalist from Kyodo News on suspicion of attempting to obtain military secrets. The journalist, who was picked up in Vladivostok, was ordered to leave the country within 72 hours.
