The defendant, who holds the rank of Captain, had worked at the Federal Office of Bundeswehr Equipment, Information Technology and In-Service Support (BAAINBw).

The Koblenz-based institution is responsible for equipping the Bundeswehr, Germany's armed forces, with equipment and weapons, as well as developing, testing and procuring defence technology.

Since May 2023, the man is said to have offered to cooperate with the Russian consulate general in Bonn and the Russian embassy in Berlin on several occasions and on his own initiatives.

Prosecutors say that the defendant, who is identified only as Thomas H due to Germany's strict privacy laws, handed over information with the intent it be used by Russian intelligence. There are no indications that he received money in return.

Details about what information he may have passed along have not been revealed.

Germany has been one of Ukraine's biggest military supporters in the face of Russia's ongoing invasion. The country's security authorities say that they have stepped up their efforts to combat espionage by Russian services.

Federal police officers took the Captain into custody in Koblenz last August. Prosecutors pressed charges in March.

His trial is to begin at the Dusseldorf Higher Regional Court at 0900 (GMT).