Seven member of the Syrian White Helmets rescue group were shot dead by unknown gunmen on Saturday, sparking a manhunt and deep suspicions in the rebel-controlled province of Idlib.

The men were killed in their operations centre in the village of Sarmin at dawn on Saturday. Two of their vehicles as well as several of their distinctive white helmets were stolen, the group said.

Many White Helmet volunteers have been killed in airstrikes during the six year Syrian war but opposition activists said it was the first time that members had been shot dead like this.

Photographs from the scene showed the volunteers’ bodies lying across the floor of the centre and blood splashed over the logo of the White Helmets group. All had been shot execution-style at close range.