syria rebels
© Khalil Ashawi / ReutersRebel fighters gather as they advance towards Azaz city, northern Aleppo countryside, Syria
At least 20 people, mostly Syrian rebel fighters, have reportedly been killed in a car bomb blast at the Free Syrian Army-controlled checkpoint cloase to a border crossing between Syria and Turkey.

Witnesses told Reuters that the blast took place several kilometers away from the Bab al Salam border crossing at a checkpoint controlled by rebel group Jabhat al Shamiya, part of the Turkish-backed FSA involved in Ankara's anti-Islamic State (IS, formerly ISIS/ISIL) operation in northern Syria.

According to Turkish news outlet, Haber Turk, the blast killed 30, as well as leaving dozens injured. It said the attack was carried out by IS terrorists. At least six wounded people were reportedly delivered to hospitals in the nearby Turkish town of Kilis.

Rebels from the loosely-organized FSA coalition, which also includes some not so "moderate" groups, are fighting alongside Turkish troops in an Ankara-led Euphrates Shield offensive operation.

The Euphrates Shield started on August 24 when Turkish forces crossed into northern Syria under the pretext of pushing Islamic State away from the border. However, besides IS, Turkey targeted the Kurdish YPG militia, which is part of the US-backed Syrian Democratic Forces (SDF).

The Syrian government condemned the operation as a breach of sovereignty and an outright invasion, while Ankara insisted that Syrian territorial integrity remains "essential" for Turkey.