An online video released Saturday night purports to show an ISIS militant behead Japanese journalist Kenji Goto, ending days of negotiations by diplomats trying to save the man.


The video, released on militant websites and highlighted by militant sympathizers on social media sites, bore the symbol of the Islamic State in Iraq and Syria group's al-Furqan media arm.


Though the video could not be immediately independently verified by The Associated Press, it conformed to other beheading videos released by the extremists, who now control a third of both Syria and neighbouring Iraq in its self-declared caliphate.


The video, called "A Message to the Government of Japan," featured a militant who looked and sounded like a militant with a British accent who has taken part in other beheading videos by ISIS. Goto, kneeling in an orange prison jumpsuit, said nothing in the roughly one-minute-long video.


Goto was captured in October, after he travelled to Syria to try to win the release of Haruna Yukawa.


The hostage drama began last week after militants threatened to kill Goto and Yukawa in 72 hours unless Japan paid $200 million US.


Jordan and Japan reportedly conducted indirect negotiations with the militants through Iraqi tribal leaders.