Two German men been charged with high treason for gathering state secrets from Germany's BND foreign intelligence agency and passing them to Russia, prosecutors said on Friday.

The pair, named as Carsten L. and Arthur E., are accused of working together with a Russian businessman to "procure sensitive information from the BND's portfolio" and hand it over to Russia's FSB security services.

Carsten L., an employee of the BND, was arrested in December 2022 and his accomplice was detained a month later as he arrived at Munich airport from the United States.

Carsten L. is accused of passing on documents from the BND to Arthur E., who in turn passed them on to the contact in Russia, the prosecutors said in a statement.

In September and October 2022, Carsten L. allegedly printed out or took screenshots of nine internal BND documents.

He then passed on the information to Arthur E., who took digital images of the documents to Moscow, printed them out and handed them over to the FSB.

The Russian businessman is said to have arranged the meetings in Moscow and paid for Arthur E.'s flights.

The information was classified and leaking it posed a serious risk to German security, the prosecutors said.

The FSB is said to have paid Carsten L. at least 450,000 euros ($482,000) and Arthur E. at least 400,000 euros, with Arthur E. picking up the payments in cash from Moscow.

On his way back to Germany, Carsten E. arranged for his accomplice to be "smuggled" through customs at the airport.

If found guilty of high treason, the suspects could be jailed for life.

Russia and Germany have been at odds over several cases of alleged spying since Russia's full-scale invasion of Ukraine in early 2022.

The BfV German domestic security agency in June warned against the risk of an "aggressive Russian espionage operation" as Moscow pursues its war on Ukraine.

Western sanctions against Russia and support for Ukraine's military defence meant the Kremlin had an "increased interest" in information gathering, the BfV said in its annual report.

In August, a German national working for the military was arrested on suspicion of spying for Russia.

In November 2022, a German man was handed a suspended sentence for passing information to Russian intelligence services while working as a reserve officer for the German army.