Russia's top domestic security agency says it has arrested two people suspected of passing the nation's military secrets to Ukraine.

The Federal Security Service, or FSB, said Friday that Dmitry Dolgopolov and Anna Sukhonosova were detained in Simferopol in Crimea. The FSB, the leading successor agency to the Soviet KGB, identified Dolgopolov as a member of the Russian military.

The agency said the two were passing sensitive information about the Russian navy in Crimea to Ukraine.

The suspects were later brought to Moscow, where a court sanctioned their arrests. If convicted of treason, they could face up to 20 years in prison.

Russia and Ukraine have been locked in a tug-of-war following Moscow's annexation of Ukraine's Crimean Peninsula in 2014 and support for pro-Russian insurgents in eastern Ukraine.