At least 39 people were killed on Saturday in an explosion that hit near buses carrying people evacuated from a besieged area of government loyalists, reported Syrian TV.

A war monitor put the death toll at 24 in the area controlled by opposition fighters.

The explosion, caused by a car bomb, hit the Rashideen area, a rebel-controlled district outside Aleppo city where evacuation buses carrying nearly 5,000 people from the northern rebel-besieged villages of Foua and Kfraya were stuck, causing a huge plume of black smoke, reported CBS News.

Residents from the two villages had been evacuated Friday, along with more than 2,000 from Madaya, an opposition-held town outside of Damascus besieged by government forces.

In footage aired on Syrian TV, bodies, including fighters, were seen lying alongside buses, some of which were charred and others gutted from the blast.

Personal belongings could be seen dangling out of the windows. The state TV channel said the car was carrying food aid but a rebel spokesman said the car had been parked in the area and abandoned.

A senior rebel leader said 20 fighters who guarded the buses were killed as well as dozens of passengers. He spoke on the condition of anonymity because he was not authorized to speak to the media.

Yasser Abdellatif, a member of the powerful Ahrar al-Sham group which negotiated the deal, said at least 30 rebels were killed in the explosion.

The explosion came as frustration was already mounting over the stalling evacuation process. Thousands of evacuees from the pro-government and opposition areas were stuck opposite sides of the edge of Aleppo city as rebels and government bickered over the terms for evacuating fighters.

Prior to the blast, Syrian Red Crescent teams had distributed meals to the restless evacuees, stuck in limbo after having left their homes over 30 hours earlier. Many were already voicing their dissatisfaction with the wait.