DAVID CAMERON revealed yesterday that the RAF carried out a secret drone strike in Syria which killed two British citizens fighting for Islamic State (Isis).

The Prime Minister insisted the strike was “necessary and proportionate” to stop attacks being planned on Britain.

But campaigners described it as a an “extrajudicial killing” that “violated” the will of Parliament.

Reyaad Khan from Cardiff and Ruhul Amin from Aberdeen were killed on August 21 in a precision air strike carried out by RAF drones, the PM told Parliament.

Mr Khan, the target of the strike, was killed alongside Amin and two other Isis terrorists when the vehicle they were travelling in was hit.

No civilians were killed or injured.

Mr Cameron said that it was the first time that Britain had conducted a strike in a country where it was not at war — and refused to rule out a repeat.

In a statement to the House of Commons, he insisted the act of “self-defence” was “entirely lawful.”

“The attorney general was consulted and was clear there would be a clear legal basis for action in international law,” he told MPs.

“We were exercising the UK’s inherent right to self-defence.

“There was clear evidence of the individuals in question planning and directing armed attacks against the UK.”

But the strike was condemned by the Campaign for Nuclear Disarmament as an “alarming” development that could “set a dangerous new precedent.”

General secretary Kate Hudson said: “This is extrajudicial killing — a British Prime Minister now claims the right to kill British citizens when they travel abroad.

“We must also remember that Parliament voted against strikes in Syria in August 2013.

“This latest round of strikes is a further violation of the will of Parliament.”

And Reprieve legal director Kat Craig added: “The fact that David Cameron has bypassed Parliament to commit these covert strikes is deeply worrying — as is his refusal to share what legal advice he was given.”

Mr Cameron said the latest strike was sanctioned by the National Security Council after British security forces alerted him to the threat posed by Mr Khan.

Acting Labour leader Harriet Harman demanded an independent legal analysis of the decision in a detailed scrutiny of Mr Cameron’s statement.

“Why didn’t the attorney general authorise this specific action rather than merely ‘confirming there was a legal basis for it’?” she asked.

This is the second time that the government has been accused of disregarding Parliament’s veto on British involvement in bombing in Syria.

In July it was revealed that three British pilots were embedded with US forces as part of an “operational” exchange and had taken part in bombing raids on Isis in Syria.

Mr Cameron said yesterday that the case for British involvement in bombing raids “only grows stronger,” but promised to stage a second vote on the issue before sanctioning such action.

Ms Harman said she would “carefully consider” any motion the government brought forward.

But Plaid Cymru warned against the refugee crisis being “exploited” as an excuse for bombing Syria.

“Resorting to knee-jerk military action, especially with no clear exit strategy is tantamount to pouring fuel on the fire,” said leader Leanne Wood, adding that it would “more than likely displace far more people.”