A drone entered the airspace of NATO and EU member Bulgaria and exploded near the border with Romania, Prime Minister Rumen Radev said on Saturday.
The drone exploded on Bulgarian territory about 100 metres from the Romanian border, Radev said following a meeting of the government's security council in Sofia.
There were no injuries or property damage.
Teams from Bulgaria's border police and Defence Ministry are working to determine the origin of the drone, Radev said.