MOSCOW (AP) - Russia's domestic security agency says it has arrested a U.S. citizen on espionage charges.

The Federal Security Service, or FSB, the top KGB successor agency, said that the American man detained in Moscow on Friday. The agency said in Monday's statement that he was caught "during an espionage operation," but didn't give any details.

The state Tass news agency identified the detained man as Paul Whelan. Spying charges carry a prison sentence of up to 20 years in Russia.

The U.S. Embassy in Moscow had no immediate comment.

The arrest comes as Russia-U.S. ties have sunk to post-Cold War lows over the Ukrainian crisis, the war in Syria and the allegations of Russian meddling in the 2016 U.S. presidential election.

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