Around 50 people have been killed and 80 more injured in a massive auto bombing Saturday in the rebel-held city of Azaz in northern Syria, local activist Mahmoud Hassano told CNN.
As the death toll rose, local hospitals put out an emergency call for blood donors and Turkish media outlets reported that 23 people had been carried across the border for treatment.
There was no immediate claim of responsibility for the bombing.
Azaz is a major stronghold of the Turkish-backed Free Syrian Army (FSA), an alliance of moderate opposition groups whose fighters have, with Turkish military support, largely pushed Daesh militants out of the border area near Turkey. Al-Bab is one of the two targets of Euphrates Shield, with the other one being the town of Manbij controlled by YPG-dominated Syrian Democratic Forces (SDF).
Dozens were also wounded in the attack near a government complex and market area, the UK-based Syrian Observatory for Human Rights said.
It is also sandwiched between rival groups, including Kurdish fighters to the west and Turkey-backed opposition groups to the east.
Its opposition-affiliated media center said Saturday that search-and-rescue operations continued for hours after the blast, which shattered the facade of a local courthouse. Bodies were strewn on the ground as a father ran away from the scene hugging his child.
Syria's almost six-year war has created a patchwork of areas of control across the country, and Azaz is a major stronghold of the Turkish-backed Free Syrian Army (FSA). The Islamic State group and al-Qaida-linked group Fatah al-Sham Front are not included in the deal, according to the Syrian government.