A former US Marine detained in Russia has been charged with espionage, the Interfax news agency reports.
Russia's FSB state security service detained Paul Whelan, 48, in Moscow last Friday on suspicion of spying, in a case that threatens to aggravate diplomatic tensions with the United States.
Whelan could face up to 20 years in prison if convicted.
Paul Whelan of Michigan who has been arrested in Moscow, Russia by the FSB under charges of espionage. Source: Supplied
The FSB opened a criminal case against Whelan but gave no details of his alleged espionage activities.
Interfax said the Russian authorities had brought formal charges against Whelan on Thursday, citing what it described as an informed source.
Reuters could not independently verify the Interfax report.
Whelan's lawyer Vladimir Zherebenkov declined to comment on the charges but told Reuters that under the terms of the arrest order, Whelan was expected to remain in custody in Moscow until at least February 28.
"I consider his detention and arrest baseless," Zherebenkov told Reuters by telephone.
"It's based on investigators' supposition that he will hinder the investigation process. We are asking for bail instead."
US Secretary of State Mike Pompeo said on Wednesday the United States had asked Russia to explain Whelan's arrest and would demand his immediate return if it determines his detention is inappropriate.
Whelan's family has said he was visiting Moscow for the wedding of a retired Marine and is innocent of the espionage charges against him.
Under Russian law, espionage can carry sentences of 10-20 years in prison.
Zherebenkov said Whelan, who is being held at the Lefortovo detention facility in Moscow, was "feeling positive" and that a translator was explaining the legal procedures to him.
"All his rights and all international principles are being fully followed," Zherebenkov said.
