Many in northern Iraq expected the extremist group
On Thursday, as ethnic Kurds prepared to celebrate the holiday, the group's supporters posted a video on social media accounts that appeared to show the beheading of three fighters from the Kurdish Peshmerga militia.
The Peshmerga have emerged as a key member of the U.S.-led coalition battling Islamic State, helping to recapture territory seized by the militants with the help of airstrikes.
The six-minute video, titled "The Response of the Defiant to the Shelling by the Tyrants," opens with scenes of bloodied civilians seeking treatment in hospitals and of the destruction in residential areas.
The scene then abruptly switches to the all-too-familiar image of a prisoner in an orange jumpsuit being led by a black-clad militant. The Kurdish-speaking captor says Islamic State is not against the Kurdish people but "those who accepted to ally with the crusaders and [Iranians] to wage war on the Muslims."
The scene repeats twice more with a different prisoner and captor. The Iraqi Kurdish leader, Massoud Barzani, is blamed for what happens next. The three militants are shown raising their knives high into the air. They then grab their prisoners by the chins and begin sawing into their necks.
The authenticity of the video could not immediately be verified.
The video identifies the victims as Lance Cpl. Hisham Nabil Khorsheed, Pvt. Bashtawan Rasoul and Pvt. Razgar Saleh.
One of the Kurdish-speaking militants shown is believed to be Khaled Hamo, whose tribe denounced him as a traitor in a Facebook posting Thursday and disowned him for "sullying the reputation of the tribe."
The Peshmerga have been waging a campaign against Islamic State since August, when the group's militants seized large parts of northern Iraq and threatened the capital of the semi-autonomous Kurdish region, Erbil.
The fate of the fighters, who were captured along with 14 of their comrades in Kirkuk province in January, has been the subject of intense speculation in recent weeks. Their families have called on the Kurdish leadership to do more to free the prisoners.
The prime minister of the Kurdish region, Nechirvan Barzani, said in February that there had been "serious attempts" to secure their release but would not elaborate.
In the video, Islamic State militants accused Kurdish officials of lying about attempts to negotiate with the group.
"The fate of this apostate is the same fate that awaits dozens of captives who are being held from among your soldiers by the Islamic State, if you return to your stupidity once again," one of them says.