This undated file photo provided by the Whelan family shows Paul Whelan in Iceland. (PHOTO / Courtesy of the Whelan Family / AP)

MOSCOW - A Russian court found ex-US marine Paul Whelan guilty of spying for the United States on Monday and sentenced him to 16 years in jail, a move the US ambassador to Moscow called an egregious violation of human rights that would harm ties.

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

Whelan, who holds US, British, Canadian and Irish passports, has been in custody since he was detained by agents from Russia’s Federal Security Service in a Moscow hotel room on Dec 28, 2018.

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Russia says Whelan, 50, was caught red-handed with a computer flash drive containing classified information. Whelan, who pleaded not guilty, said he was set up in a sting and had thought the drive, given to him by a Russian acquaintance, contained holiday photos.

US Ambassador to Russia John Sullivan told reporters after the verdict that no evidence had been produced to prove Whelan’s guilt and demanded he be released immediately.

“His conviction is a mockery of justice,” said Sullivan.

He said the ruling would not have “a good influence” on already poor ties between Moscow and Washington, but that dialogue would continue.

Vladimir Zherebenkov, Whelan’s lawyer, said his client had been told when detained that he would be part of a prisoner swap with a Russian national held in the United States.

When asked about such an idea, the Russian Foreign Ministry told the RIA news agency it had proposed prisoner swaps to the United States many times but gave no further details.

Moscow has repeatedly called on Washington to secure the release of two Russian nationals - convicted arms dealer Viktor Bout and Konstantin Yaroshenko, a pilot serving 20 years in the United States for conspiracy to smuggle cocaine into the country.

Zherebenkov said Whelan had no objection to the idea of formally asking Russia to pardon him, something that if granted could secure his release.

READ MORE: Russia says it caught ex-US marine accused of spying red-handed

Whelan will serve his sentence in a maximum security prison, Moscow’s city court said. His trial was closed because authorities said it involved the discussion of state secrets.

State prosecutors, who accused Whelan of being at least a ranking US military intelligence colonel, had asked the court to sentence Whelan to 18 years in a maximum security prison.