A court in Moscow extended the detention of accused spy and former U.S. Marine Paul Whelan by three months Friday, one of his attorneys told CBS News.

Vladimir Zherebenkov said the court ordered Whelan held until May 28, when he's to appear in court again.



Russia's Federal Security Service (FSB) sought the extension.

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Whelan, who has U.S., British, Canadian and Irish citizenship, denies the charges against him.

The British Broadcasting Corporation reports Whelan was brought to court Friday in handcuffs and looking downcast. When asked how he was, "He paused and gave a weak smile but no comment," the BBC said.

Paul Whelan in photo provided by his family on January 1, 2019 Handout

Whelan was detained in Moscow at the end of December while there for a wedding, his family has said. On January 22, a Russian court rejected his bid for release on bail. His detention was instead extended until Feb. 28 pending a trial on the espionage charges, according to the state-run Interfax news agency.

U.S. intelligence and State Department sources have told CBS News they're confident Whelan isn't a spy.

Whelan's family, which also denies the accusations against him, says Zherebenkov was chosen for him.

Zherebenkov told CBS News' Elizabeth Palmer outside the court when Whelan was arraigned that Whelan was found at his hotel at the time of his arrest with a flash drive containing Russian "state secrets." He didn't, however, explain how Whelan came to be in possession of the information on the drive and said his client wasn't aware that the Russian government considered the material sensitive.

"I've worked as an investigator for 20 years and if I do have a smoking gun, I will then put my strongest card on the table, to crush the opponent. In this case I don't see any smoking gun," Zherebenkov said after the hearing.

He added that the prosecution doesn't "have strong evidence to back up the charges."

Whelan has worked for a Michigan-based auto parts company since 2017. He is currently its global security director. He had spent 14 years in the U.S. Marine Corps before being discharged in 2008 for bad conduct, according to the military.