The US military said Friday it was "reasonably certain" that it killed the Islamic State militant known as "Jihadi John" in a drone strike in Syria. 

"We are reasonably certain that we killed the target that we intended to kill, which is 'Jihadi John,'" Colonel Steven Warren said from Baghdad in a briefing that was webcast live to reporters at the Pentagon.

The masked British militant targeted in Thursday's strike had appeared in a string of grisly videos showing the execution of Western hostages.