NATO member Romania reported a Russian drone hit a 10-storey block of flats in the southeastern city of Galati overnight, injuring two people.
The incident marked the first time a drone had hit a densely populated area in Romania and caused injuries, increasing tensions on NATO's eastern flank.
Romania scrambled two F-16 fighter jets and a military helicopter to monitor the attack, and the pilots were authorised to shoot down any drones.
Two people were receiving medical treatment on site, while 70 people had evacuated the building.
A woman and her child were taken to hospital with minor injuries, and two others were treated on site for panic attacks.
The drone's entire explosive payload detonated, and the fire was extinguished.
