Syria's opposition says the bodies of some 65 men and boys executed with their hands bound have been found in the city of Aleppo.
According to rebels and the U.K.-based Syrian Observatory for Human Rights, the victims were killed with a single gunshot to the head or neck.
Rebels said the bodies were recovered in the Quweig River on January 29.
The rebels blamed the Syrian regime for the killings.
In a separate development, activists said Syrian rebels captured a government intelligence compound in the eastern city of Deir el-Zour early on January 29 after five days of heavy fighting.
The rebels reportedly freed several prisoners held in the compound.
It remains unclear whether the prisoners are fighters or activists.
Deir el-Zour is located in an oil-rich area near the Iraqi border.
Based on reporting by AFP, Reuters, and AP