© Reuters / Maxim Shemetov
Paul Whelan, the ex-US Marine suspected of espionage in Russia, had documents containing state secrets at the time of his arrest in Moscow, his lawyer said. Whelan may not have been aware he had sensitive information, he added.

"I can confirm that at the time of his detention, Whelan had some documents containing state secrets, but I cannot go into details," Vladimir Zherebenkov, who represents Whelan, told reports on Tuesday.

Zherebenkov, however, suggested that his client may have been unaware that he was in possession of the secrets. "How he got it, what he was supposed to do with it, and whether Whelan knew that he had secret information is unknown," he said.

The former US Marine was seeking information on Russia of an "open" and "cultural" kind, the lawyer said, suggesting that his efforts were inspired only by his keen interest in Russian heritage.

"Whelan has been interested in Russia, he received education in culture studies, he has friends in Russia, so there is nothing surprising that he was keen to get information of cultural interest," he said.

The problem arises from a flash drive that Whelan received, which contained the state secrets in question. His lawyer says the former Marine was only expecting to get data on Russian culture, including photos of Orthodox cathedrals. He claims that Whelan didn't even have time to download the files.

The comments were made shortly before Whelan appeared before the Moscow City Court in a bid to secure his release from prison on bail. The court rejected the motion, ordering that Whelan should remain in pre-trial detention through February 28.

Russian authorities claim that Whelan, who was reportedly in Moscow to attend a wedding, was caught "red-handed" in an act of espionage. The US citizen also holds British, Canadian and Irish passports.

Zherebenkov spoke to reporters after the court hearing, telling them that there was no 'smoking gun' in the case, and that even state prosecutors have not been given access to the secret evidence being used to charge Whelan.

He left open the possibility that his client could be released in a spy swap with the United States.