Intelligence chiefs are investigating claims the ISIS fake jihadi who led the executions of 21 Egyptians was an American recruit.
The militant, who spoke English with a U.S. accent, appeared in a horrific video on Sunday showing the beheadings of a group of Coptic Christians on a beach in Libya.
Brandishing a knife, he declares: 'All crusaders... the sea you have hidden Sheikh Osama bin Laden's body in, we swear to Allah we will mix it with your blood.'
The men are then forced to lie face-down before they are beheaded simultaneously.
U.S. officials are understood to be analysing the militant's facial features and speech patterns as has been done in the hunt for the British executioner known as Jihadi John, who has appeared in a number of beheading videos in Syria.
Professor Erik Thomas, a linguistics expert at North Carolina State University, believes he 'sounds like an American' with some Arabic influence, based on some of word pronunciations.
Another U.S. specialist, who asked not to be named told ABC News that he may be a native Arabic speaker who learned English by spending 'a significant amount of time' in America.
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