Ambulances and fire brigades are working on the scene of the explosion, local media reported.
At least 40 civilians, 11 children among them, were killed and 47 injured when a fuel truck exploded in the Syrian city of Afrin, the Turkish Defence Ministry said.
Earlier, a local source said that 23 people were killed and 26 injured in an explosion in central Afrin.
The source added that local hospitals were calling on its residents to donate blood.
A video and photos of the aftermath of the alleged explosion were shared online.
According to the Syrian Observatory for Human Rights (SOHR), the explosion happened when a car bomb detonated at Raju road in central Afrin.
Ambulances and fire brigades have arrived at the scene of the explosion, the Anadolu news agency said.
The Turkish Defence Ministry has blamed the explosion on the Syrian Kurdish YPG (People’s Protection Units) militia which Ankara sees as a terrorist group linked to Kurdish militants on its territory. Earlier this year, Turkey launched a military operation in northern Syria to push YPG militants back from the border. On 18 March, Turkish President Erdogan announced that the mainly Kurdish city of Afrin was seized from the YPG.