Kurdish Peshmerga fighters stand guard at Mosul Dam in northern Iraq Reuters

Islamic State militants have beheaded a Kurdish man and released an execution video entitled "A message in blood to the leaders of the American Kurdish alliance".

In an attempt to send a stern warning to the Kurdish forces, which are battling the Sunni insurgents in Iraq, the group has also shown 14 other Kurdish men dressed in orange jumpsuits and standing under the Isis flag.

Three armed Islamist militants are seen standing behind the Kurdish man brandishing a knife near Mosul's iconic mosque.

"Any mistake of recklessness from you will lead to the [loss] of our life," one of the men has been quoted as saying in the video footage.

The video was first uploaded to YouTube but was later removed. However, the execution video continues to surface.

The latest images come on the heels of the radical group publishing pictures of slaughtering dozens of Syrian soldiers.

The jihadist group claimed the troops were captured and executed shortly after a Syrian airbase was seized last week.

A caption on the video read: "The 250 shabeeha taken captive by the Islamic State from Tabqa in Raqqa have been executed."

The Britain-based Syrian Observatory for Human Rights has put the number of executed at 120.