The video, titled "a message in blood to the leaders of the American-Kurdish alliance," opens with 15 men in orange jumpsuits standing around the ISIL flag.
Three of the men ask Kurdish president Massud Barzani "and the Kurdish government to end their relationship with the US... military intervention in northern Iraq," the SITE Intelligence Group monitoring service said.
"Any mistake or recklessness from you will lead to the (loss) of our life," SITE quoted one of the men as saying.
The video then cuts to three masked men dressed in black standing in front of a mosque with another man wearing an orange jumpsuit kneeling in front of them. They then behead him, AFP reported.
The video follows another released by the ISIL showing the beheading of American journalist James Foley and threatening another kidnapped reporter Steven Sotloff with the same fate if US air strikes are not halted.