The video, which was posted online on Monday, shows the terrorists pouring a flammable liquid on the hand-cuffed, blind-folded men who appear to be Syrian Kurdish soldiers.

The militants then push the three into a fire they have made.

Reports said that al-Nusra militants attacked Tal Abyad district of Raqqa governorate in northern Syria on Monday, killing 450 civilians. The victims were said to be women, children and the elderly.

Fighting between Kurdish militia and al-Qaeda-linked militants has been escalating in north and northeastern Syria in the past weeks after Kurdish fighters, who are opposed to foreign interference in Syria, managed to push back the militants from several positions in the area.

On July 30, a powerful Kurdish militia said it was mobilizing against al-Qaeda-linked groups in northeastern Syria following the killing of a Kurdish opposition leader in the area.

"We call on the Kurdish people... to step forward.... Anyone fit to bear arms should join the ranks of the Committees for the Protection of the Kurdish People (YPG) and to face the assaults of these armed groups," said a YPG statement, which was released shortly after the assassination of Isa Huso in al-Qamishli.

Syria has been gripped by deadly unrest since 2011. According to reports, the Western powers and their regional allies -- especially Qatar, Saudi Arabia, and Turkey -- are supporting the militants operating inside Syria.

According to the United Nations, more than 100,000 people have been killed and a total of 7.8 million displaced due to the violence.

BA/BA