David Cameron
David Cameron Reuters

British Prime Minister David Cameron said Friday it was not yet clear whether the Islamic State (ISIS) terrorist known as "Jihadi John" had been killed in a US airstrike in Syria.

Cameron said the strike had targeted British citizen Mohammed Emwazi, but added: "We cannot yet be certain if the strike was successful," in a statement delivered outside his Downing Street office.

He added: "This was an act of self-defense, it was the right thing to do."

The Pentagon announced Thursday that an air strike targeting Emwazi, a computer programmer who grew up in London, took place in Raqqah, ISIS's de facto Syrian capital.

Emwazi featured in videos showing the brutal beheadings of US journalists Steven Sotloff and James Foley, US aid worker Abdul-Rahman Kassig, British aid workers David Haines and Alan Henning, Japanese journalist Kenji Goto and other hostages. 

AFP contributed to this report.