Amnesty International and a Syrian group are charging that gunmen have executed captured men believed to include Syrian soldiers, calling it "shocking."
The British-based Syrian Observatory for Human Rights says the killings occurred near the northern town of Saraqeb.
An amateur video appears to show rebels executing captured Syrian soldiers. The rebels beat and kick the soldiers, some of whom were wounded, before shooting them dead.
The authenticity of the video could not be independently confirmed. The video is consistent with other AP reporting in the area.
On Friday the Observatory condemned the killing of nearly a dozen soldiers at the Hmeisho checkpoint. Amnesty released a highly critical statement.
Rami Abdul-Rahman, who heads the Observatory, asked how rebels can demand rights at a time when they violate such rights.