The brother of a US citizen arrested in Russia on espionage charges says he's innocent and was in Moscow to attend a wedding.
Paul Whelan was arrested in Moscow on Friday. The Russian Federal Security Service, in announcing the arrest three days later, said Whelan was caught during an espionage operation but gave no details.
"We are deeply concerned for his safety and well-being," his brother, David Whelan, said in a statement posted on Twitter on Tuesday.
"His innocence is undoubted and we trust that his rights will be respected."
The Russian spying charges carry a prison sentence of up to 20 years.
He said the family last heard from Paul Whelan, a retired Marine, on Friday, "which was very much out of character for him, even when he was travelling".
The state department said on Monday it had received formal notification from the Russian foreign ministry of the arrest and was pushing for consular access.
The department did not identify Whelan at the time or provide any information about the case, citing "privacy considerations".
David Whelan told CNN his brother, who had served in Iraq, has been to Russia many times in the past for both work and personal trips, and had been serving as a tour guide for some of the wedding guests.
He apparently disappeared on Friday and his friends filed a missing persons report in Moscow, his brother said.
David Whelan told the news channel that the family was relieved at first when they heard he was in custody.
"It's knowing that he's not dead, it weirdly really helps," he said.
The arrest comes as US-Russian ties are severely strained, in part over Russian meddling in the 2016 presidential election.
Former CIA Moscow station chief Daniel Hoffman said it was "possible, even likely" that Russian President Vladimir Putin had ordered Whelan's arrest to set up an exchange for Russian gun-rights activist Maria Butina.
Butina is in US custody after admitting she acted as a secret agent for the Kremlin in trying to infiltrate conservative US political groups as Donald Trump was seeking the presidency.
She pleaded guilty in December to a conspiracy charge as part of a deal with federal prosecutors.
Russian President Vladimir Putin has claimed the case is fabricated and that Butina entered the guilty plea because of the threat of a long prison sentence.
