Serbia has arrested eight foreign citizens, including two Americans and two Ukrainians, on suspicion that they tried to photograph and enter military facilities without authorization, officials said.

State-run RTS TV said the U.S. and Ukrainian citizens allegedly tried to take shots of the military intelligence headquarters in downtown Belgrade with a drone.

The report did not identify them or give details, saying only that the Ukrainians are women and that they are all in police custody.

Announcing the arrest of the eight foreigners on February 19, Serbian Defense Minister Aleksandar Vulin said he did not want to prejudge the case that is under investigation, but added, "It is not a coincidence that such a large number of foreign citizens tried to bust into premises controlled by the Army of Serbia."

Another American was arrested in Serbia earlier this month for possession of an unmarked gun. Pro-government media alleged that he was a former U.S. Navy SEAL and had planned the assassination of unidentified Serbian officials.

Serbian President Aleksandar Vucic on February 18 mentioned the arrest of a "group" of foreigners, but said that their case was "not particulary dangerous."

"We recently had a bit more serious case, but today's one does not seem to be on that level," he said.

Based on reporting by AP and AFP