The death of the extremist known as Jihadi John (above) in an air strike has yet to be confirmed but the Pentagon is increasingly confident. British Prime Minister David Cameron described it as an “act of self-defence”. Photo: Reuters

The Pentagon is “reasonably certain” the extremist known as “Jihadi John” has been killed in an air strike. US military spokesman Colonel Steve Warren said it would take “some time” to confirm the death of the notorious British killer – real name Mohammed Emwazi – who was targeted in Islamic State’s Syrian stronghold.

British Prime Minister David Cameron has hailed the apparent death of Jihadi John as a “strike at the heart” of the extremist group. But British Labour leader Jeremy Corbyn said it would have been “far better” if Emwazi had been brought to justice in the courts for his “callous and brutal crimes”.

Mr Cameron said the US drone attack targeting Emwazi was an “act of self-defence” and “the right thing to do”.

He was backed by the chairman of the Intelligence and Security Committee (ISC), who said there was a “sound legal basis” for the air strike in the Syrian stronghold of the terror group, which is also known as Isil or Daesh.

In a statement delivered outside 10 Downing Street, Mr Cameron stressed it was not yet absolutely certain that the “barbaric murderer” was dead.

Britain and our allies will not rest until we have defeated this evil terrorist death cult

“If this strike was successful – and we still await confirmation of that – it will be a strike at the heart of Isil,” he said. “And it will demonstrate to those who would do Britain, our people and our allies harm, we have a long reach, we have an unwavering determination, and we never forget our citizens. “Britain and our allies will not rest until we have defeated this evil terrorist death cult and the poisonous ideology on which it feeds.”

The air strike targeting Emwazi was carried out in Raqqa, the IS stronghold in Syria, on Thursday night. ISC chairman Dominic Grieve told BBC Radio 4’s World At One: “It’s always better if somebody is guilty of a serious crime that they should be brought to justice through the ordinary legal process but in this case it was clearly impossible for that to happen.”