Two Swedish men accused of spying for Russia went on trial on Friday.

The men, Peyman K., who is 42 years old, and his brother, Payam K., who is 35 years old, appeared before the Stockholm District Court Friday.

They face charges of having "jointly" passed information to Russia's military intelligence agency, the GRU, for a decade between 2011 and 2021, according to the charge sheet.

The two are alleged to have acquired data through jobs with Sweden's domestic security service, or SAPO, and the country's armed forces. The data originates from several authorities within the Swedish security service. 

Swedish broadcaster SVT quoted an intelligence expert as explaining that the case appeared to be one of the most damaging cases of espionage because the men compiled a list of all the employees who worked for SAPO.

What do we know about the case?

Peymen K. was arrested in September 2021 and his brother in November 2021. Both have denied any wrongdoing, their defense lawyers told the court.

If found guilty, the men could face life imprisonment. The brothers are of Iranian origin and later became naturalized in Sweden, according to Swedish media outlets.

The trial is mostly taking place behind closed doors because of the sensitivity of the case.

"The case is unique in many ways," prosecutor Mats Ljungqvist told the court in his opening statement. "We haven't had a trial like this in more than 20 years."

The information obtained was "extremely sensitive material," Ljungqvist said. 

"The court will have insight into material that very few in this country have seen or have access to," he added.

Swedish security service says preliminary investigation opened in 2017

SAPO earlier this month said it became suspicious of the former employee and a preliminary investigation was launched in 2017.

Ljungqvist also said earlier this month that the inquiry was started "because there was a suspicion that there was a mole, an insider" within Sweden's intelligence community.

He added that much of the information in the preliminary investigation is secret and could not offer details.

One of Sweden's largest spy scandals took place during the Cold War when Stig Bergling, a Swedish security officer who worked for both SAPO and the armed forces, sold secrets to the Soviet Union.

He was sentenced in 1979 to life imprisonment on similar charges and later escaped while serving his time.

Editor's note: Deutsche Welle follows the German press code, which stresses the importance of protecting the privacy of suspected criminals or victims and urges us to refrain from revealing full names in such cases.

rm/ar (AP, AFP)