A US drone strike targeted a vehicle in Syria believed to be transporting the masked Islamic State militant known as "Jihadi John", according to US officials.

However, whether the strike killed the British man who appears in several videos depicting the beheadings of Western hostages was not known, British Prime Minister David Cameron said Friday.

Mohammed Emwazi was the target of an airstrike in Raqqa, Pentagon press secretary Peter Cook said in a statement. Officials were assessing the results of the strike, he said.