Both are reported to have worked for security services, and one was a senior manager at a government agency when arrested last year.

Investigators have seized mobile phones, a smashed hard drive and notes detailing cash and gold transactions.

The suspects deny any wrongdoing, their defense lawyers have told local media.

Peyman Kia, 42, and Payam Kia, 35, are believed to have worked together to pass on information to Russia’s military intelligence service, the GRU.

The men were arrested in late 2021 and have been in custody ever since.

While both are accused of aggravated espionage, Peyman Kia has also been charged with the gross unauthorized handling of secret information.

The chief prosecutor of Sweden’s National Security Unit, Per Lindqvist, described the case as very difficult to investigate, adding the men were suspected of “highly serious criminality targeted at Sweden’s intelligence and security system”.

The secret information — which could result in “detriment to Sweden’s security” in the hands of a foreign power, according to Lindqvist — was reportedly gathered while the older Kia was employed at Sweden’s security services and army.

Newspaper Dagens Nyheter said the suspect also served in the Office for Special Acquisition (KSI), a top-secret organ of the country’s intelligence services.

When arrested last November, Peyman Kia was reportedly a security chief at the Swedish Food Agency.

During Peyman’s arrest, his younger brother Payam “dismantled and broke a hard drive that was later found in a bin”, according to the charges.

Payam is thought to have managed contact with Russia and the GRU including “matters of surrender of information and receipt of compensation”.

Much of the information from the preliminary investigation has not been released due to its sensitive nature.

The older Kia’s defense lawyer, Anton Strand, told Sweden’s public broadcaster SVT the charges were imprecise and lacked “concrete” descriptions of his client’s alleged crimes.

Björn Sandin, defending the younger suspect, similarly suggested the charges demonstrated that prosecutors were “not entirely confident” about their claims, according to TV4.

If convicted, the brothers may be handed life sentences — generally a minimum of 20-25 years in prison in Sweden.