Islamic State militants have released a video which appears to show a Kurdish man being beheaded in Iraq.

The six-minute video is titled "A Message in Blood" and shows men wearing orange jumpsuits who are said to be Kurdish fighters captured by IS.

One man is later seen kneeling outside a mosque in the city of Mosul before he is beheaded. The jihadists have warned that the other fighters will be killed if Kurdish leaders continue to back the US.

One of the captured men said: "Any mistake or recklessness from you will lead to the (loss) of our life."

It comes after US President Barack Obama called for a coalition of countries prepared to take military action against IS.

Mr Obama said the US was working to get more countries on board in order to strike at the jihadist group.

He said: "We are going to work politically and diplomatically with folks in the region, and we're going to cobble together the kind of coalition that we need for a long-term strategy as soon as we are able to fit together the military, political and economic components of that strategy."

Mr Obama played down the prospect of imminent US military action in Syria, saying "we don't have a strategy yet", but said it was time for Middle Eastern nations to "stop being ambivalent".

France has already ruled itself out. The UK has so far provided humanitarian assistance and British Prime Minister David Cameron has said he does not want troops on the ground.

'Soldiers executed'

On Thursday, another IS video emerged showing hundreds of "executed" Syrian soldiers. The soldiers were captured at the weekend when the Sunni militants seized an air base in the province of Raqqa, in northern Syria.

The Reuters news agency said the video, which was posted on YouTube and shows dozens of bodies, had been confirmed as genuine by an IS fighter.

"Yes we have executed them all," he said.

The video shows the bodies of scores of men wearing nothing but their underwear lying face down. The line of bodies appears to be dozens of metres long.

A caption written underneath says: "The 250 shabeeha taken captive by the Islamic State from Tabqa in Raqqa have been executed."

Shabeeha is the name of armed militia forces loyal to President Bashar al Assad. Tabqa is the location of the Syrian airbase captured by IS in the last few days.

The head of the Syrian Observatory for Human Rights later confirmed that Syrian soldiers had been "executed" at three different places, resulting in the deaths of at least 160.

Rami Abdel Rahman said it had happened after jihadists defeated the 1,400-strong garrison at Tabqa, of whom 200 were killed in fighting, 700 escaped and dozens of the remainder were captured as they fled.