ALEPPO, Syria: The unidentified bodies of 29 people, found along with dozens more in a river in Aleppo after being shot at close range, were buried in a common grave on Thursday to vows of vengeance.

They were among an estimated 80 young men, women and children who had been shot in the head or neck at point-blank range by unknown killers and dumped in the river, where they were found on Tuesday.

The bodies, which had lain unclaimed in a makeshift morgue at a school in the Bustan al-Qasr district of Syria's once-thriving commercial capital, were loaded aboard five trucks and taken to a park, an AFP correspondent said.

The remaining victims had already been identified by relatives and taken home for burial.

The funeral cortege was accompanied by a crowd that swelled to 2,000 by the time it reached what has been renamed the River Martyrs Park, where the bodies were placed in a trench 18 paces long and two metres (6.5 feet) deep.

The park was chosen as a burial site because there was no cemetery available where they could all be buried in the same place, said Ahmed Shama, a rebel commander in Aleppo who vowed vengeance for their deaths.

The rebels of Aleppo "have decided that in less than 24 hours they will provide a forceful response to this slaughter," he said.

"We have promised the families of these people that their deaths will not be in vain ... We will avenge each and every one of these martyrs."

After the funeral prayers were complete and an excavator covering the trench with earth, rebel Free Syria Army soldiers urged mourners to leave the park for their safety. Moments later, bullets fired by regime snipers began slamming in to buildings next to the park and people fled.

No one has claimed responsibility for the gruesome massacre. Rebels fighting to overthrow President Bashar al-Assad blame his regime, and it in turn points the finger at the rebel Islamist Al-Nusra Front.

The United Nations says that more than 60,000 people have died in the 22-month uprising against Assad.