On Saturday, A vehicle filled with explosives hit the bus convoy from government-held towns near Aleppo, Syria.
The Syrian Observatory for Human Rights said 98 evacuees were killed, along with rebel soldiers and aid workers.
According to the several reports, Children were also among the dead.
The observatory group said, many more have been injured and the death toll is expected to rise.
The blast shattered coaches and set cars on fire, leaving a trail of bodies, as the convoy waited in rebel territory near Aleppo, Syria.
Images from the scene showed bodies lying on the ground outside devastated and blackened vehicles.
The BBC’s Middle East correspondent Lina Sinjab said, it happened when a vehicle loaded with food arrived and started distributing crisps, attracting many children, before exploding.
She also said it wasn’t clear how the vehicle could have reached the area without government permission.
But there is also no proof that rebels were involved in the attack, as the government claims.
It wouldn’t be in the rebels’ interest, our correspondent says, as they were waiting for their own supporters to be evacuated from the other towns.
The planned evacuation was part of the so-called “four towns” deal, where civilians in towns under siege by both sides would be allowed to leave.
It applies to government-controlled Kefraya and Foah, where the bomb struck, as well as rebel-held Zabadani and Madaya near Damascus.
There were fears of revenge attacks on evacuees from rebel-held towns, being moved under a deal.