At least 40 civilians were killed, including 11 children, when a bomb detonated on an oil tanker in the northern Syrian town of Afrin on Tuesday, the Turkish Defence Ministry said, blaming the attack on the Syrian Kurdish YPG militia.

In a statement on Twitter, the ministry said the blast occurred in a crowded area in Afrin’s center. A video shared by the ministry showed black smoke billowing in the air while ambulance and police sirens wailed in the background.

Ankara views the YPG as a terrorist group linked to Kurdish militants on its own soil and has mounted military operations in northern Syria to push it back from the border.

Turkey’s military and its Syrian rebel allies seized Afrin, a mainly Kurdish district, from the YPG in March 2018 in a major offensive.

Tuesday’s blast was one of the deadliest to hit a region under the control of Turkish-backed forces. Ankara frequently blames the YPG for the attacks, while the militia says it does not target civilians.