Malta-based NGO Migrant Offshore Aid Station (MOAS) has evacuated one of its bases in Ukraine after it was struck by Russian weapons in the early hours of Saturday morning.

The attack left some of its staff with minor injuries and two of its ambulances damaged, the organisation said in a statement on Saturday afternoon.

The blast, which the NGO said could have been caused by a rocket or drone attack, detonated “just three metres away from the building,” smashing windows and causing a large fire in several of the rooms.

Expensive medical equipment and medical supplies were destroyed in the fire, it said.

The NGO said it was not yet clear whether its base had been targeted intentionally or come under fire by mistake but noted that another four targets also came under fire in the same town during the attack.

It said the 19 medical staff and other personnel in the building at the time moved to the building’s bomb shelter, with “minor injuries sustained from flying debris.” Eight other staff members of the NGO were out on call at the time, it said.

MOAS stressed it was just the latest in a series of incidents affecting its medical staff, who it said were “facing more injuries from the frontline” as Russia’s offensive in eastern Ukraine continued.

However, it said it was the first time the NGO had been directly hit after around two and a half years operating on the frontlines, where it undertakes evacuations of wounded soldiers and transports them to hospital.

MOAS founder Christopher Catrambone called the incident an “unfortunate setback” for the organisation, but said it “strengthens our resolve” to continue operating in the conflict.

“Our thoughts are with our brave medics and personnel - and their families - who have risked their lives daily, for the past two and a half years, to help give a fighting chance to some of the most seriously wounded victims of this war”, he said.

The organisation has assisted more than 45,000 seriously wounded soldiers in Ukraine and more than 200,000 worldwide since its inception in 2014, it said.

Saturday’s attack comes just days after Russia launched a “massive" attack on Ukraine's power grid.

On Monday, Russia fired hundreds of drones and missiles at the embattled country, killing at least four people and causing widespread blackouts, officials said.