London (AFP) - Britain warned Russia on Friday against playing "diplomatic chess games" after Paul Whelan, a former US Marine who reportedly also carries Canadian and Irish passports, was charged with espionage.
Foreign Secretary Jeremy Hunt said Britain had offered consular access to Whelan, who was detained in Moscow last week, but had not been able to visit him yet.
"We are giving him every support that we can, but we don't agree with individuals being used in diplomatic chess games," Hunt told the BBC in an interview.
"It is desperately worrying, not just for the individual but their family, and we are extremely worried about him and his family as we hear this news," he said.
US ambassador Jon Huntsman visited Whelan at the Lefortovo prison in Moscow on Wednesday.
The United States has been cautious in its public comments on the case, with Secretary of State Mike Pompeo saying earlier that Washington was trying to learn more about the situation.
Whelan, 48, was arrested last Friday "while carrying out an act of espionage", according to Russia's FSB domestic security service.
The charge carries a maximum jail sentence of 20 years.
US news reports painted Whelan as an unlikely spy with a chequered history who most recently worked for the security service of an international auto parts manufacturer.
Whelan was court-martialled by the Marine Corps in 2008 on charges of larceny and passing bad checks, The New York Times said, an offence that in most cases disqualifies candidates from foreign intelligence work.
He was arrested while attending an American friend's wedding to a Russian woman at Moscow's upscale Metropol Hotel, according to his twin brother David.
His family has denied he is a spy, with his brother calling the possibility "inconceivable".
- Collecting passports -
The New York Times said Whelan has been travelling regularly to Russia since 2006 and made friends with Russians through his social media account in VK, the local version of Facebook.
He also appears to have developed a penchant for collecting passports, with his case now implicating four Western countries.
Whelan also holds an Irish passport, although he entered Russia on his US one, an official source told AFP.
The Irish foreign ministry said it has "requested consular access to an Irish citizen currently detained in Russia after receiving a request for assistance".
The Russian foreign ministry said Britain's request to see Whelan "is being worked on".
And The Washington Post said Whelan also carries a passport from Canada, where he was born.
"He collected (passports) as a game," the Post quoted a person familiar with Whelan's case as saying.
"There was an ongoing competition with his sister to see who could get the most."
Diplomatic relations between Britain and Russia are tense, particularly following the attempted murder of a former Russian spy in Britain last year with a nerve agent.
Britain accused Russia of being behind the attack despite Moscow's denials, and coordinated the expulsions of dozens of Russian diplomatic staff around the world.