The Latest on developments in Syria (all times local):

11 a.m.

The Islamic State group has claimed responsibility for a deadly bombing in a northwestern Syrian village that killed at least 20 people, including many Turkey-backed opposition fighters.

The IS-linked Aamaq news agency says a suicide car bomber struck a convoy of rebels on the Syrian side of a border crossing point in the village of Atmeh.

The Britain-based Syrian Observatory for Human Rights said the blast killed at least 20 people and wounded dozens. An activist collective in Idlib province known as Ariha Today put the death toll at 24.

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10:30 a.m.

Syrian activists have raised the death toll from an explosion in a northwestern village near the border with Turkey to at least 20 killed, including Turkey-backed rebels.

The Britain-based Syrian Observatory for Human Rights says the blast in Atmeh on Thursday morning was either caused by a suicide bomber or a remotely detonated bomb. Another group, the Local Coordination Committees, says the blast was caused by a bag filled with explosives that went off on the Syrian side of a border crossing.

An activist collective in Idlib province known as Ariha Today says the blast killed 24.

The Observatory says the killed rebels have been fighting along with Turkish forces against the Islamic State group since August.

No one claimed responsibility for the attack.