isis has publicly beheaded six men accused of exploding a car bomb ` which killed innocent people ' in the syrian city of al-mayadin .
the terrorist group 's latest barbaric video shows a large crowd gathering to watch the bloody execution of the men it claims are soldiers fighting for syrian president bashar al-assad .
they are all marched to a small wooden stump and instructed to kneel , before an islamic state militant carries out brutal retaliation .