Islamic State (IS) has published a video purporting to show the beheading of three Kurdish peshmerga fighters in northern Iraq by militants, who threatened to kill "dozens" more of those being held captive.

The six-minute clip showed the peshmerga wearing orange jumpsuits being decapitated by three black-clad militants, all of whom spoke Kurdish.

"To the Muslim Kurdish people: know that our war is not with you, rather it is with those who ventured into an alliance with the Safavids and crusaders to wage war on the Muslims," said one of the militants, using derogatory terms to refer to Iran and the coalition respectively.

Another of the militants then directly addressed Kurdish leader Masoud Barzani: "We warned you before that for every rocket you fire on those under the care of the Islamic State, you will kill one of your prisoners with your own hands."

Earlier this year, a peshmerga was beheaded by a Kurdish militant in Mosul after Grad rockets were fired into the city by the Kurds.

Last month, another video was published showing captive peshmerga in cages being interviewed by a Kurdish militant.

(With inputs from Reuters)