A trial is underway in Sweden in the case of two Iranian-born Swedish brothers charged with spying for Russia and its military intelligence service GRU for a decade.

Peyman Kia, 42, and Payam Kia, 35, appeared before the Stockholm District Court to face accusations they worked together to pass information to Russia between September 28 2011 and September 20 2021.

Between 2014 and 2015, Peyman Kia worked for Sweden’s domestic intelligence agency but also for Sweden’s armed forces.

Sweden’s prosecutors allege the data they gave the Russians originated from several authorities within the Swedish security and intelligence service, known by its acronym Sapo.

Swedish media said Peyman Kia worked for the armed forces’ foreign defence intelligence agency, whose Swedish acronym is Must, and reportedly worked with a top secret unit under Must which was dealing with Swedish spies abroad.

Intelligence expert Joakim von Braun told Swedish broadcaster SVT as the trial opened that even though many details remain unknown, it appeared to be one of most damaging cases of espionage in Sweden’s history because the men compiled a list of all Sapo employees.

“That alone is a big problem because Russian intelligence focuses on human sources,” Mr von Braun said.

Peyman Kia was arrested in September 2021 and his brother in November 2021. Both deny wrongdoing, their defence lawyers told the court.

Payam Kia helped his brother and “dismantled and broke a hard drive which was later found in a trash can” when his brother was arrested, according to charge sheet obtained by the Associated Press (AP).

The naturalised Swedish citizens face sentences up to life imprisonment if convicted.

In another case, Swedish authorities on Thursday released one of two people arrested this week on suspicions of spying against Sweden and another foreign power, but said the freed person remains a suspect.

The two were arrested on Tuesday in a predawn operation in the Stockholm area.

Authorities have given few details about the case, but Swedish media cited witnesses who described elite police rappelling from two Black Hawk helicopters to arrest them.

According to the Swedish reports, the two were a couple and are Russians who arrived in Sweden in the late 1990s.

The AP could not confirm these reports.

The investigation had been under way for some time, Sapo said.

It said one of those arrested was suspected of aggravated espionage against Sweden and against “a foreign power”.

Authorities did not identify the other country allegedly spied on.

Authorities in Sweden said that case is not related to other cases of espionage.