Syrian rebels have executed at least 20 Syrian soldiers, according to a new video released by the London-based Syrian Observatory for Human Rights, a pro-rebel outlet. The video showed blindfolded soldiers with their hands tied behind their backs executed over the weekend in eastern Aleppo.

The video also showed the bodies lined up after the executions, with at least 20 slain soldiers shown. The rebels in the video cheered for the camera and taunted the bodies of the captives.

Human rights groups were critical of the move, saying the killings were carried out by the Free Syrian Army (FSA) the largest and most heavily Western-backed of the various rebel factions in the nation.

Navi Pillay, the UN Human Rights Commissioner, called the killings an “extra-judicial execution” and expressed concern about the rebels’ growing use of torture as well as IED attacks.