Romanian news site Digi24 reports suspicions of several drones in the area.
The first drone was discovered in the coastal city's civilian port on Friday morning and exploded, the Defense Ministry said in a statement, according to AFP.
The sea drone is "a type used in the war in Ukraine" and is not part of the Romanian defense arsenal, the ministry said, according to Digi24.
The port has reportedly been put on alert, residents have been urged to leave their homes and an investigation has been launched.
The incident comes just days after a Russian drone crashed into an apartment building in the Romanian city of Galati, injuring two people.
