The police had "arrested eight foreign citizens for either trying to shoot images of military sites without authorisation or to enter" them, Defence Minister Aleksandar Vulin said in a statement.

Vulin gave no details on the nationality or identity of those arrested.

Serbia's state-run RTS television reported that two US and two Ukrainian nationals were arrested for allegedly trying to film using a drone the building that houses military intelligence.

Serbian President Aleksandar Vucic said late Sunday that the case was "not particularly dangerous".

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

Vucic was referring to the arrest in Belgrade earlier this month of a US citizen who illegally possessed a gun. The case was apparently not linked to the arrests reported Monday.