A Moscow court on Tuesday extended the detention of former U.S. marine Paul Whelan, a Canadian-American citizen, until March 29 on espionage charges, Interfax news agency reported.

Whelan, who holds U.S., British, Canadian and Irish passports, was detained in December 2018 and accused of spying.

Agents from Russia's Federal Security Service detained Whelan in a Moscow hotel room on Dec. 28 last year and accused him of spying.

Moscow says he was caught with a computer flash drive containing classified information.

Whelan says he was set up in a sting and had thought the drive, given to him by a Russian acquaintance, contained holiday photos.

He has been held in pretrial detention while investigators look into his case.

Whelan was born in Ottawa to British parents and moved to the U.S. as a child.

Diplomats from Canada, the U.S., Ireland and the U.K. — all the countries Paul Whelan holds passports for — will visit a Moscow prison where the former U.S. marine has been held for more than a year now on spying charges. The “Christmas visit” comes amid concerns that Whelan’s health is worsening. 2:03

When he was arrested, he was director of global security and investigations for Michigan-based auto-parts maker BorgWarner. Prior to that, worked in security and investigations for the global staffing firm Kelly Services, which is headquartered in Michigan and has operations in Russia.

Whelan also holds Irish citizenship.

Bart Gorman, U.S. deputy chief of mission, made a pre-Christmas appeal to Russia to free Whelan on Monday outside a Moscow prison after he and diplomats from Britain, Canada and Ireland also had visited the Michigan native.

"In a case where there is no evidence and no crime, it's time to have him released," Gorman said.

Gorman said Whelan was in "reasonably good spirits," but Whelan's repeated requests to telephone his parents had not been granted.