TALLINN (Reuters) - Estonia has detained a man suspected of being a Russian agent operating against the Estonian state, the prosecutor’s office said on Tuesday.

The man was stopped at the weekend as he prepared to leave Estonia for Russia from the north-east border town of Narva. He was formally charged on Monday in a Tallinn court.

“A person, who is a Russian citizen, is suspected of acting as an FSB agent in the preparation of a computer crime against the Republic of Estonia,” the prosecutors office said. “The target of his action against Estonia was the Estonian state authorities.” No further details were given.

Russia’s Federal Security Service, or FSB, is a successor to the KGB, the Soviet Union’s security service.

Neither the FSB nor the Russian Foreign Ministry immediately replied to requests for comment.

Estonia, occupied by the Soviet Union until 1991 but now a member of NATO and the European Union, has a strained relationship with its powerful neighbor.

In May this year, Estonia expelled two Russian diplomats posted at Moscow’s consulate in Narva for contacts with local officials that were considered inappropriate for diplomats.

Earlier in the same month, an Estonian court handed out a five-year prison sentence to a Russian national for spying for the foreign intelligence unit of the Russian armed forces.