The Islamic State group's notorious masked executioner known as "Jihadi John" has reportedly been filmed unmasked in Syria for the first time. The 27-year-old British computer programmer-turned Islamic State executioner Mohammed Emwazi has - in a newly released video - vowed to return to Britain with the ISIS leader and "carry on cutting off heads," reported Mail on Sunday.

"I am Mohammed Emwazi. I will soon go back to Britain with the Khalifa (ISIS leader)... We will kill the kuffar (non-Muslims)... I will carry on cutting heads," Emwazi said in a one-minute-17-second video obtained by the Daily Mail on Sunday from the Syrian army.

Emwazi, in the chilling video, is seen wearing a black hood with his face uncovered for the first time on camera.

"I have noted a number of apparent similarities in both the morphological and the proportional comparisons and in my opinion the images lend support to the contention that they are the same person," a British expert on facial mapping said, according to i24 News.

British Prime Minister David Cameron ordered British security agencies to speed up their efforts to capture or kill Emwazi following the release of the video, according to Mirror.

Jihadi John has reportedly beheaded at least seven foreigners in Syria, including Britons David Haines and Alan Henning. He was last seen beheading Japanese journalist Kenji Goto at the end of January, HNGN reported previously.