The bodies of young men and boys were found in the Quweiq River, which separates Bustan al-Qasr district from Ansari, in Aleppo’s southwest.
The area is under the control of the foreign-backed militants who are seeking to overthrow the government of President Bashar al-Assad.
Some of the bodies had their hands tied behind them and the others appear to had been shot in the head.
A senior security source said many of the victims had previously been reported kidnapped.
He blamed the terrorists of carrying out the executions.
President Bashar Assad recently promised to uproot what he described as an al-Qaeda offshoot in Syria.
On January 21 a suicide bomber blew up an explosives-packed truck in a town outside Hama killing 42 people asd injuring 165.
Syrian troops are fighting insurgents who are reportedly trying to take control of the government’s intelligence complex and a prison in the east of the country, an NGO reports.
The Britain-based Syrian Observatory for Human Rights says opposition forces have attacked an intelligence complex in the city of Deir el-Zour and freed some eleven inmates from a prison, where opposition activists are being held.
The bodies of dozens of young men, all apparently executed with shots to the head, were found on Tuesday in a river in a rebel zone of Syria's Aleppo city, the Syrian Observatory for Human Rights said.
A rebel Free Syrian Army captain at the scene confirmed the discovery, saying that at least 68 bodies had been found and that many were still being dragged from the water.
Voice of Russia, Press TV, Interfax, AFP