SEOUL, South Korea (AFP) — Seoul is providing “necessary consular assistance” to a South Korean national who has been detained in Russia, Seoul’s foreign ministry said Tuesday, reportedly on espionage charges.

Seoul’s foreign ministry on Tuesday declined to give details on the South Korean’s detention, citing an ongoing investigation.

“Upon learning of the arrest, the local diplomatic mission has been providing necessary consular assistance,” it said.

Russia’s state-run TASS news agency first reported that a South Korean man had been detained earlier this year on suspicion of espionage and was being held in a Moscow prison.

TASS, which said the case was “top secret,” identified the suspect as Baek Won-soon and said he had been picked up in Russia’s far-eastern city of Vladivostok.

“According to a TASS source in law enforcement agencies, Baek Won Soon passed state secret information to foreign intelligence services,” the agency said.

It is the first time Russia has arrested a South Korean citizen for criminal espionage, according to TASS.

Baek was transported from Vladivostok to Moscow for further investigation and is being held in the capital’s notorious Lefortovo prison, the Russian news agency added.