A marine drone – similar to the ones used in the Ukraine war – has caused a major explosion after hitting the main port of Constanța in NATO state Romania.

Despite it being isolated, footage showed smoke rising from the unmanned boat in the Black Sea port which had ‘self-detonated’ at around 10:30am local time.

The Black Sea port was being urgently evacuated amid fears of three more sea drones approaching, with residents nearby warned to take cover – however no casualties have been confirmed.

It was not immediately clear who the green-coloured drone belonged to, however the Romanian authorities stressed it did not belong to the Romanian armed forces.

Romania shares a shares a 400-mile border ​with ⁠Ukraine, with the civilian and naval port around 100 miles south of this boundary.

‘The maritime drone is of the type used in the war in Ukraine,’ said the NATO state’s defence ministry.

‘The situation is dynamic and we will return with information and official data as they become available.’

The explosion came after the sea drone had been ‘secured and isolated’ by forces of the Romanian Intelligence Service, the Coast Guard and the Ministry of National Defence. Evidently a timer was set to explode.

A marine drone – similar to the ones used in the Ukraine war – has caused a major explosion after hitting the main port of Constanța in NATO state Romania

The unmanned boat had ‘self-detonated’ at around 10:30am local time and it was not immediately clear who the green-coloured drone belonged to

An ‘extreme’ RO Alert issued with an order to evacuate people within a one kilometre radius amid reports ‘three more maritime drones heading towards the port’.

The alert stated: ‘Evacuate the area within a radius of 1 km in the coastal area of the Port of Constanta.

‘Stay calm! Take shelter in cellars or civil protection shelters.

‘In the absence of shelter, stay inside the house, away from windows and external walls.’

Interior Minister Raed Arafat said: ‘We ​now know there is the risk of self-detonation, we have … evacuated in case there are more drones,’ Arafat ​said.

‘We are not panicking, the measures are purely ​preventative.’

An emergencies chief said: ‘There is a possibility that there may be other drones in the area, which is why the RO Alert message was issued for Constanţa and Tulcea counties.

‘We decided to preventatively evacuate the coastal area for one kilometre until we ensure that there is no risk of another explosion.’

Romanian Prime Minister and President Nicușor Dan were urgently informed about the incidents, said reports. A criminal investigation is now underway.

The explosion was near the headquarters of the Romanian Agency for Saving Human Life at Sea in the civilian part of the port.

The main NATO land battlegroup in Romania is French-led and also includes troops from Belgium, Spain and Luxembourg.

Other NATO forces also rotate through or operate in Romania, including U.S. troops at Mihail Kogălniceanu and Câmpia Turzii, and air-policing deployments such as the UK RAF Typhoons.

The explosion comes just days after a Russian drone crashed into an apartment block in Galati, a city in southeastern Romoania close to the border with Ukraine.

Two people were injured and it was the first time that a drone had struck a densely populated area in a NATO state during the conflict in Ukraine.