US-led coalition air strikes have hit al-Qaeda’s Syrian branch overnight, expanding the raids to jihadists outside the Islamic State group for only the second time.

The strikes against Al-Nusra Front in northwestern Syria killed several jihadists as well as two children, the Britain-based Syrian Observatory for Human Rights said on Thursday.

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Coalition aircraft carried out “several raids after midnight” targeting an Al-Nusra vehicle and one of its positions, the Observatory said.

The militant group confirmed the strikes on Twitter, saying they were carried out by “the alliance of Crusaders and Arabs on Al-Nusra positions, causing deaths, mostly of civilians”.

The Observatory said on Thursday that the coalition had also carried out strikes for the first time on another Islamist group, Ahrar al-Sham, near the Turkish border.

US and Arab nations have been carrying out air strikes against ISIL in Syria since September 23 in a bid to prevent the jihadist group from seizing more territory in the conflict-hit nation.

On the first day of the strikes they also hit a group of al-Qaeda veterans that Washington called “Khorasan”, although analysts said the attack actually targeted Al-Nusra.

There have been no reported strikes on groups outside ISIL since, but this second attack comes after Al-Nusra made gains against Western-backed rebel fighters in the northwestern Idlib region.

Al-Nusra fighters in the past week drove the Western-backed Syrian Revolutionary Front from its bastion in Idlib province and captured a town after the withdrawal of the Hazm movement, another moderate opposition group.

The advances were seen as a blow to US efforts to create and train a moderate rebel force as a counterweight to jihadists and the forces of Syrian President Bashar al-Assad.