The former U.S. Marine sentenced by a Russian court to 16 years on espionage charges reportedly has arrived in the region where he will serve his term.

Paul Whelan is being held at Correctional Colony No. 18 in the Mordovia region southeast of Moscow, Valery Krutov, the chairman of a local prison watchdog group, told Radio Free Europe.

He is expected to stay there for about two weeks before being handed over to another penal colony in the region to serve out the rest of his sentence, Krutov added.

Paul Whelan, a former U.S. Marine who was arrested for alleged spying, listens to the verdict in a courtroom at the Moscow City Court in Moscow, Russia, on June 15. (Moscow News Agency/AP)

WHELAN WILL NOT APPEAL SENTENCE AND WILL WAIT FOR POTENTIAL PRISONER SWAP, REPORT SAYS 

Both Whelan and his family have said that he is innocent and was only in Russia to attend the wedding of a friend from his time in the Marines. U.S. Secretary of State Mike Pompeo has also demanded the American be freed.

Whelan, who was arrested in December 2018, has said that he was set up -- that a person he considered a friend handed him a USB drive allegedly containing vacation photos. But minutes later, Russian authorities stormed his hotel room. Russia says the drive contained a list of names of those working at a classified security agency.

Whelan previously told AFP it's possible he's being held as a pawn in a potential prisoner swap between the U.S. and Russia.

But the Russian Foreign Ministry has denied such claims.

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The U.S. Embassy has denounced Whelan's trial in Russia as unfair, pointing out that no evidence has been provided. And his family, chiefly his brother David Whelan, has publicly defended him.

Whelan is also a citizen in Canada, Ireland and the United Kingdom.

Fox News’ Tyler Olson and the Associated Press contributed to this report.