The film is believed to be from eastern Deir al-Zor province and dates from 2012, according to the Syrian Observatory for Human Rights, an opposition monitoring group.
Observatory head, Rami Abdelrahman, said the Nusra Front has been releasing videos of past operations. He said the man seen executing the prisoners in the video – a Nusra commander – had been killed in March in battles with local tribes.
The footage shows the commander, his face covered in a black balaclava, shooting each prisoner in the back of the head as they kneeled, blindfolded, in a row in the sand.
“The sharia court for the eastern region in Deir al-Zor has sentenced to death these apostate soldiers that committed massacres against our brothers and families in Syria,” the executioner said. Islamists with black flags shouted “God is great” as each man was shot. The executioner returned to some victims, firing more bullets into them to make sure they were dead.
Videos of executions and torture have become increasingly common in Syria, where more than 94,000 people have been killed in a conflict now in its third year, according to the UK-based Observatory.
The Nusra video is the second be published in the past two days showing executions by fighters who say they are from al-Qaeda-linked groups.
A video on Wednesday from the northern province of Raqqa, which is controlled by Islamist rebels, showed three blindfolded men sitting on the kerb of a central roundabout before being shot in the head with a pistol.