Russia said Friday it had detained two of its citizens including a member of the armed forces who allegedly passed Ukraine military secrets on the Black Sea naval fleet based in Moscow-annexed Crimea.

The FSB security service said in a statement that it had detained a man who was serving in the Russian armed forces in Crimea named as Dmitry Dolgopolov and a woman named as Anna. It said the pair “had been gathering and passing to the Ukrainian special services information that is a state secret about the activities of the units and divisions of the Black Sea naval fleet” based in Crimea.