STOCKHOLM, Sweden: Two Iranian-born Swedish brothers were put on trial this week after being charged with spying for Russia and its military intelligence service (GRU).

Appearing before the Stockholm District Court, Peyman Kia, 42, and Payam Kia, 35, both naturalized Swedish citizens, faced charges of working together to pass on information to Russia from 28th September, 2011, to 20th September, 2021, while working for Sweden's domestic intelligence agency and the armed forces.

Swedish prosecutors claimed that the data they gave the Russians originated from several authorities within the Swedish security and intelligence service, known as SAPO.

Swedish media reported that Peyman Kia worked for the armed forces' foreign defense intelligence agency, known in Sweden as MUST, as well as a top secret unit within the agency that dealt with Swedish spies abroad.

In an interview with Swedish broadcaster SVT, intelligence expert Joakim von Braun said 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 had lists of all SAPO employees.

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

"The material is the absolute most secret material available. It is an unusual trial in that a similar case has not appeared in Sweden in over 20 years," prosecutor Mats Ljungqvist told the court.

Peyman Kia was arrested in September 2021 and his brother in November 2021. Their defense lawyers told the court that they both denied any wrongdoing.

They could face sentences up to life imprisonment if convicted.