File photo of David Cameron.
An RAF drone strike in Syria killed three Islamic State (IS) militants, 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.
Khan had been planning "specific and barbaric" attacks in Britain, Cameron said.
The strike had been "entirely lawful" and carried out following consultation with the attorney general, he added.
"There was a terrorist directing murder on our streets and no other means to stop them," he said.
"Is this the first time in modern times that a British asset has been used to conduct a strike in a country where we are not involved in a war? The answer to that is yes," he added.
A second British jihadist who was in the vehicle, Ruhul Amin, was also killed but no civilians were harmed, the prime minister said.
Cameron also said he supported Britain extending its anti-IS bombing campaign to Syria as well as Iraq but stressed he would return to parliament for formal authorisation to do so.
"I believe there is a strong case for the UK taking part in air strikes. I believe that case only grows stronger with the growing number of terrorist plots," he said, adding that six plots against Britain had been disrupted over the past 12 months.
Cameron's government was defeated on taking military action in Syria in 2013 in one of the most damaging foreign policy blows to his previous coalition government.
The prime minister cannot secure the necessary parliamentary approval for air strikes without opposition support due to a slim parliamentary majority and some of his own MPs being against the move.
Jeremy Corbyn, the favourite to win the leadership of the main opposition Labour Party to be announced on Saturday, is a founder of the Stop the War coalition and repeated his opposition to air strikes on Monday.
"My view is that it would create more problems than it would solve," he said.