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BEIRUT — A stalled population transfer resumed Saturday after a deadly explosion reportedly killed at least 100 people, including dozens of children, government supporters and opposition fighters, at an evacuation point — adding new urgency to the widely criticized operation.

The blast ripped through a bus depot in the al-Rashideen area where thousands of government loyalists evacuated the day before waited restlessly for hours, as opposition fighters guarded the area while negotiators bickered over the completion of the transfer deal.

Only meters away, hundreds of evacuees from pro-rebels areas also loitered in a walled-off parking lot, guarded by government troops.

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Syrian state media had said at least 39 were killed, including children.

But the opposition Syrian Observatory for Human Rights put the death toll at 126 dead, including 68 children under the age of 18 and 13 women, adding that it would likely rise because of the extensive damage.

A Facebook page belonging to the pro-government Foua and Kfraya villages said all those in three buses were killed or are still missing while a rebel official said at least 30 opposition fighters who were guarding the evacuees were killed in the blast.

The Syrian Civil Defense in Aleppo province, also known as the White Helmets, said their volunteers pulled at least 100 bodies from the site of the explosion. White Helmets member Ibrahim Alhaj said the 100 fatalities documented by the rescuers included many children and women, as well as fighters.

This frame grab from video provided by the Thiqa News Agency, shows the wreckage from a blast at the Rashideen area, a rebel-controlled district outside Aleppo, Syria, on Saturday. Thiqa News via AP

Video from the scene showed bodies, including those of fighters, lying alongside buses, some of which were charred and others gutted from the blast. Personal belongings could be seen dangling out of the windows. Fires raged from a number of vehicles as rescuers struggled to put them out.

The scenes were the latest in the unyielding bloodshed in Syria. Earlier this month, at least 89 people were killed in a chemical attack as children foaming at the mouth and adults gasping for last breath were also caught on camera.

The bloody mayhem that followed the Saturday attack only deepened the resentment of the transfer criticized as population engineering. It also reflected the chaos surrounding negotiations between the warring parties. The United Nations did not oversee the transfer deal between villages besieged by the rebels and those encircled by the government.

No one claimed responsibility for the attack but pro-government media and the opposition exchanged accusations, each pointing to foreign interference or conspiracies undermining the deal.