Russia's state-run media say a Japanese journalist was expelled last month for trying to obtain secret information relating to its military capabilities in the Far East.

Reports say the man was detained in Vladivostok on December 25, received a warning and was given 72 hours to leave the country. He is said to have returned to Japan the next day.

The Russian Foreign Ministry reportedly summoned a Japanese embassy official in Moscow to lodge a protest.

Tokyo-based Kyodo News acknowledged that a reporter who was covering Russian authorities was detained and interrogated on December 25. It says it believes the man was engaged in ordinary activities as a journalist.
The Russian media reports follow Japanese police investigating a suspected espionage case in Tokyo involving Russian diplomats.

Tokyo police arrested a former employee of telecom giant SoftBank on Saturday on suspicion of stealing the firm's trade secrets. He reportedly said that he gave the information to a Tokyo-based official of Russia's Trade Representation.

Japanese police have made a request to question the official, along with another diplomat who has since returned to Russia.

The Russian Embassy in Tokyo criticized Japan over the case, saying it regrets that "Japan has subscribed to the fashionable anti-Russian speculation in the West on the worn-out topic of spying."