At least 43 people were killed in a car bomb explosion in the Syrian border town of Azaz on Saturday, reported AP. Several people were injured in the blast that took place outside a courthouse. The town in the northern province of Aleppo is around 7 km from the Turkish border, and it is under the control of the rebel forces.

Rami Abdurrahman, the head of the Syrian Observatory for Human Rights monitoring group, said the explosion was caused by a rigged water or fuel tanker. He said six rebel fighters died in the incident. The town is home to several rebel fighters were were pushed out of Aleppo in December.

The attack has yet to be claimed by a militant group. The Islamic State group has, in the past, orchestrated several attacks in the town, which was under the group’s control in 2013, reported BBC. The incident comes in the middle of a ceasefire agreement recently reached between the rebels and the pro-government forces.

The Syrian Army recaptured Aleppo from the rebel fighter in December 2016, announcing the end of the four-year battle. Russia and Turkey helped the Bashar al-Assad government take back the city, though they have been accused of widespread human rights violations in the process.