This appears to be one of the biggest massacres to have taken place in Aleppo.
A video filmed by one of the rescuers and posted online on Tuesday shows rows of bodies, most of them young men, with their hands tied behind their backs and single bullet wounds to their heads. The graphic footage shows blood seeping from the corpses across silt left on a concrete plain by recent floodwaters that have since receded into the canal below.
Rebel groups at the scene say they expect the final death toll could reach 120.
The bodies were found on Tuesday morning in a viaduct area of Bastan al-Qasr, in the south centre of the city. The area is near one of several frontlines that divide opposition groups in the east and south of Aleppo and loyalist forces in the north.
Where the men were executed is not yet clear. Winter rains have flowed strongly through the canal in recent weeks and initial assessments suggest the bodies could have been carried some distance by currents.
The Syrian regime blamed "terrorist gangs" for the killings, a term it uses for all groups fighting against it. A regime official in Damascus suggested rebels were leading a recovery in an attempt to "cover for their crimes".
"We will disclose the identities of those killed as soon as we are able to secure the bodies, which is a difficult process since the area is in the hands of terrorist groups," a Syrian official said.
Rebel groups instead blamed the regime for the killings, suggesting some of the victims had crossed into loyalist areas then disappeared. None of the dead had identification cards.
A witness to the recovery effort said several bullets had been fired during the day from buildings to the north.
Identifying bodies
Residents of rebel-held east Aleppo have reportedly arrived at the site were the bodies were found in an attempt to identify missing relatives.
The remains were loaded onto trucks and taken to the nearby Zarzur hospital where rebel officials tried to make formal identifications.
Extra-judicial killings have occurred with increasing frequency in many parts of Syria over the past six months. But Tuesday's death toll in Aleppo is believed to be without precedent since rebel groups stormed the city on July 19.
In the months since then, the opposition has been entrenched in the east of the city and the regime has hunkered down in the north-west. The south-west suburbs of Seif al-Dawli and Salahedin remain battleground areas. Few residents cross the divide, which is manned on one side by Syrian soldiers in sniper postition and on the other by rebel groups. – Guardian News and Media 2013