MOSCOW -- The lawyer for an American man being held in Moscow on suspicion of spying said on Tuesday that his client was given a flash drive containing Russian "state secrets" before he was arrested, but did not know he had them and had not looked at them.
His family insisted that he was entrapped and denied that he is guilty of espionage.
Paul Whelan, a former U.S. Marine, was detained in Moscow at the end of December. The arrest raised speculation that he could be swapped for one of the Russians held in the U.S., such as gun rights activist Maria Butina, who has pleaded guilty to acting as a foreign agent in the U.S.
Whelan made his first public appearance in court on Tuesday to hear the appeal of his arrest. The judge upheld the previous ruling that ordered him to be kept behind bars at least until the end of February.
Whelan was kept in a glass cage and did not speak to reporters.
Spying charges carry a prison sentence of up to 20 years in Russia.
Whelan's lawyer, Vladimir Zherebenkov, said Tuesday that when his client was detained at a Moscow hotel at the end of December he had something with him that contained "state secrets."
The lawyer said that Whelan was a frequent visitor to Russia and that he asked an unnamed person to email him something about travel around the country. Whelan reportedly was not able to download it and then asked that person to put it on a flash-drive.
"He was expecting to see on the flash drive some personal information like pictures or videos, something like that, about that person's previous trips around Russia," Zherebenkov told reporters. "We don't know how the materials that contain state secrets ended up there."
The lawyer said the American was detained before he could open the files. He added that it was not clear what has happened to the person who reportedly gave the flash drive to Whelan.
Zherebenkov said the investigators have not yet disclosed which country he is accused of spying for.
Paul Whelan's twin brother, David, said in a statement that the family was disappointed but hardly surprised by the denial of bail.
"While we still lack any details from the Russian government about why Paul is thought to be a spy, and who provided him with the alleged state secrets, we are certain that he was entrapped and is not guilty of espionage," he said in a statement. "We have not had any information about a USB drive, what was on it, or how it might have materialized in Paul's possession."
"Unfortunately, today's ruling merely confirms that Paul will remain wrongfully detained for many more months," Whelan's brother said, adding that "Paul was able to let us know that he is worried about some health conditions and his ability to communicate with prison medical staff."
He added that his brother is "also concerned about translator support and his ability to present his defense in English."
David Whelan noted that the Russian authorities' refusal to allow British diplomats to visit his brother in prison and the cancellation of a U.S. consular visit last week raised additional concerns, but said that Canadian diplomats were scheduled to visit Thursday.
Whelan holds U.S., Canadian, British and Irish citizenships.
Whelan, 48, was discharged from the Marines for bad conduct. He works as the global security director for a U.S. automobile parts manufacturer and lives in Michigan. His family has said he was in Moscow to attend a wedding.
Vladimir Isachenkov in Moscow contributed to this report.