A British-American citizen held on espionage charges in Moscow has said a Russian agent framed him by slipping a flash drive with sensitive information into his pocket before he was arrested.

Former US Marine Paul Whelan, 48, was detained by FSB agents at his room in the Metropole hotel near the Kremlin in December with a flash drive that allegedly contained state secrets.

His lawyer previously said he believed he was receiving photographs from a trip he had taken to a town of ancient cathedrals during his extensive travels in Russia.

Mr Whelan, who holds American, British, Irish and Canadian passports and worked as a security specialist for a US-based auto parts company, said he travelled to Russia for a friend's wedding.

On Tuesday, Mr Whelan told journalists at a court hearing that he had gone an excursion to the Kremlin and returned to change for the wedding.

A person he had known for 10 years but who was actually an FSB agent “turned up at my room and put something in my pocket, then I was arrested,” he said.