Massacre video puts pressure on the US

An Islamic State video of the mass execution by firing squad of 250 Syrian soldiers has put pressure on the US to take military action.

The group released a video this week appearing to show the murder of the Syrian soldiers.

The captured troops were shown being forced to run through the desert in their underwear before facing a firing squad. Their near-naked corpses were then shown lying face down in a long, snaking line at the foot of a sandbank.

The video, posted on YouTube late this week, was confirmed as genuine by an Islamic State fighter in comments to Reuters. A caption in the video identified the captives as Syrian troops who had been defending an air base in Tabqa, about 30km from Islamic State's main stronghold in the city of Raqqa in northeast Syria. Talking to Reuters on the internet, an Islamic State fighter in Raqqa said: "Yes, we have executed them all."

This latest atrocity is likely to increase international pressure on the US to take decisive military action against the group, which claimed responsibility last week for the beheading of US journalist James Foley.

Earlier this week, the UN accused Islamic State of carrying out many mass executions in the past few months, including the killing of 670 inmates of a prison in the Iraqi city of Mosul in June and the murder of captured Iraqi soldiers.

The executed Syrian soldiers are understood to have been defending one of the Syrian government's last military outposts in northeast Syria, which fell after days of heavy fighting.

According to the British-based Syrian Observatory for Human Rights, which monitors the conflict using sources on the ground, the soldiers had been trying to flee the air base when they were captured.

The video showed men walking in their underwear while jihadist gunmen taunt them and force them to sing Islamic State slogans.

One captive, who identified himself as a Syrian army officer, is shown being subjected to interrogation and abuse after admitting he is an Alawite, the minority Shia Muslim sect.

"Who's your father? You can't possibly know who your father is. You're a bastard," the interrogator says. He then asks why the officer did not defect from the army. When the officer insists that he would simply have been conscripted again, the interrogator replies: "They would have sent you right back to the army? And we're going to send you right back to hell by slaughter."