The US military is "reasonably certain" that the militant known as Jihadi John was killed in an air strike targeting the notorious British killer.
US military spokesman Colonel Steve Warren said it would take "some time" to confirm the death of the militant - real name Mohammed Emwazi - who was targeted in the Syrian stronghold of Islamic State (IS).
Col Warren, the spokesman for the operation tackling IS, said it was not an "exact science" but the intelligence gave the US "great confidence" that the individual targeted was indeed Emwazi, who he described as the "face" of IS.
"Now we are using the same intelligence capabilities to verify that the individual we killed was in fact Jihadi John," Col Warren said.
A spokesperson for the White House in Washington said families of hostages who were killed in Syria were contacted before the US Strike.
Although Emwazi was not thought to be a major tactical figure within the ranks of IS, his appearance in a series of videos apparently showing the brutal murder of several hostages meant he had propaganda value for the extremist group.
Emwazi came to notoriety in a video in August 2014 which showed the beheading of US journalist James Foley.
He also appeared in videos showing the killings of UK hostages Alan Henning and David Haines, American journalist Steven Sotloff, aid worker Abdul-Rahman Kassig and Japanese journalists Kenji Goto and Haruna Yukawa shortly before they were killed.
The British Prime Minister David Cameron said the US drone attack targeting Emwazi was an "act of self-defence" and "the right thing to do".
"If this strike was successful - and we still await confirmation of that - it will be a strike at the heart of Isil," Mr Cameron said.
The air strike targeting Emwazi was carried out in Raqqa, the IS stronghold in Syria, last night.
Emwazi appeared in the videos dressed in black with only his eyes visible, and spoke with a British accent as he went on anti-western rants to the camera while wielding a knife.
It was not until February this year that the jihadist was unmasked as Kuwaiti-born Emwazi, who lived in the UK since the age of six.
It emerged that Emwazi had been known to British intelligence services, but managed to travel to Syria in 2013.
