MOSCOW — A retired Norwegian border inspector arrested in Russia last year on suspicion of spying probably had been acting as a courier for a Norwegian intelligence agency, his attorney said.

The man, 62-year-old Frode Berg, has been in jail in Moscow since December, stoking anger and confusion in the Arctic Norwegian border town where he lived and was known as an ardent supporter of closer ties with Russia. Some of his backers said Berg may have unwittingly cooperated with Norwegian spies or become the victim of a Russian effort to manufacture a scandal involving a strategically key U.S. ally. 

But in a phone interview Tuesday, Berg’s Oslo-based attorney, Brynjulf Risnes, lifted some of the mystery surrounding the case. Berg increasingly came to believe that he was cooperating with Norway’s military intelligence service as he agreed to mail envelopes containing cash and spy instructions during trips he made to Russia, Risnes said. 

But the lawyer said Berg’s Norwegian intelligence contacts failed to make clear the risks involved and pressured him to continue acting as a courier even after he grew hesitant. Berg faces a years-long prison term in Russia if convicted, and his supporters are calling on the Norwegian government to negotiate his release

“We are quite convinced that this is a real Norwegian spy story,” Risnes said. “The Russians caught them with their trousers down, so to speak.”

Berg’s case remains under investigation in Russia, and no charges have been filed, a Norwegian Foreign Ministry spokesman said, adding that he was unable to discuss details because of confidentiality rules. A spokesman for the Norwegian Defense Ministry, which oversees the military intelligence agency, declined to comment. 

Berg’s case was the subject of a front-page Washington Post report in February and has shaken his town, Kirkenes, which has worked to maintain a close economic and cultural relationship with Russia despite growing strains between Moscow and the West. Berg’s attorneys have gone public with new details in recent days in part because they expected the information to be leaked by Russian authorities anyway, Risnes said. 

An acquaintance of Berg’s linked to Norwegian military intelligence at some point introduced him to a man in Oslo who asked Berg to carry some envelopes with him on his trips to Russia, Risnes said. Berg frequently traveled to Russia and helped organize cross-border projects such as an annual art festival and a ski race

Berg was aware that the envelopes each contained 3,000 euros in cash, Risnes said. They were to be delivered via regular Russian mail. It is not clear who the recipient was. In all, Risnes said, Berg carried out the operation two to five times. 

“I feel really misused,” Berg said in a Moscow court appearance this year. “I have been fighting against hate and anger.”

Risnes said his client, who is married and has two children and five grandchildren, sensed that he was doing something connected to intelligence and “got cold feet.” In response, Risnes said, Berg’s contact in Oslo — a man named Jorgen — pressured the retiree to continue, using phrases such as, “Don’t you want to be a good Norwegian?” 

“They never disclosed to him how dangerous this was,” Risnes said. When Berg went to Moscow in December, again carrying 3,000 euros, he “thought, ‘This is the last time.’ Of course, sitting where he sits now, that was a very disastrous thought.” 

In Kirkenes, a Barents Sea port 15 minutes from the Russian border, a banner that says “Help Frode home!” still hangs in the center of town, people there said. His supporters hope a spy exchange could bring him back, although Risnes said he knew of no convicted spy imprisoned in Norway who could be used in such a deal. 

“To be realistic, I don’t think that will happen for a lot of time — for many years,” Kirkenes pastor Torbjorn Brox Webber, a member of a Berg support group, said of the possibility of such a deal. “I’m as shocked as everyone else.”