An RAF drone strike has killed three Daesh (IS) militants in Syria, two of them British, Prime Minister David Cameron said Monday, the first time Britain has carried out such an attack.

"In an act of self-defence... Reyaad Khan was killed in a precision air strike carried out on August 21 by an RAF remotely piloted aircraft while he was travelling in a vehicle in the area of Raqqah in Syria," he told parliament.