The FBI are closing in on American ISIS executioner after a wave of 'substantial leads' following a public appeal for help in identifying him. The unknown man, who has appeared in a propaganda video released by the terror group, is believed to be from the United States because of his pronounced American accent. Today a senior FBI official told ABC News that new leads possibly included a man with a 'North American' accent who appeared in the clip. Scroll down for video The FBI are closing in on American ISIS executioner after a wave of 'substantial leads' following a public appeal for help in identifying him
@highlight
FBI released a portion of a mid-September ISIS propaganda video
@highlight
The video features a man believed to be North American
@highlight
Bureau reached out to the public asking for help identifying the man
@highlight
In the video, the jihadist spoke while Syrians dug their own graves
@highlight
FBI Director: Dozen Americans are believed to be fighting alongside ISIS
'We continue to call on the public to report suspicious activity of travelers in support of a terrorist organization or information about the subject speaking with a @placeholder accent in the video issued by ISIL on September 19.