BEIRUT: Syrian state media blamed the Islamist rebel Nusra Front for the killing of dozens of people in the northern city of Aleppo, contradicting activist accounts which blamed President Bashar al-Assad's forces for the bloodshed.

The victims' families "have identified a number of the killed, stressing that the Nusra Front abducted them because of their refusal to cooperate with this terrorist group," state news agency SANA said.

Opposition campaigners said Assad's forces had committed a massacre on Tuesday after at least 65 people were found shot dead with their hands bound alongside the Queiq River in Aleppo's rebel-held Bustan al-Qasr neighbourhood.

They posted a video of at least 51 muddied male bodies, with what looked like bullet wounds in their heads. The activists said the men had been executed and dumped in the river before floating downstream into the rebel area.

SANA's reporter said the water level in the river was too low to carry the bodies any distance suggesting they had been killed in the rebel-controlled area.

Syria restricts access to independent media, making it difficult to verify accounts from activists and officials.