"FSB officers arrested a serviceman of the Western Military District in the Voronezh region on suspicion of committing a crime under Article 275 of the Russian Criminal Code (High treason)," the FSB said in a statement.
The soldier was arrested on the order of the Voronezh garrison military court.
According to the statement, the man was recruited by the Ukrainian military intelligence. He collected information about the activities of the Russian Armed Forces, and this leakage could have damaged the country's defence capability.