US-led air strikes hit Qaeda branch in Syria: monitor

US-led coalition air strikes hit Al-Qaeda's Syrian branch overnight, hitting militants outside the Islamic State (IS) group for only the second time, a monitoring group said on Thursday.

The raids also for the first time targeted the Ahrar al-Sham rebel group, a militant brigade that is part of a key armed opposition front.

The strikes against Al-Qaeda affiliate Al-Nusra Front in north-west Syria killed several militants as well as two children, the Britain-based Syrian Observatory for Human Rights said.

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 also said Thursday that the coalition had carried out strikes for the first time against Ahrar al-Sham, near the Turkish border.

The group is one of Syria's largest armed opposition groups and is part of the key Islamic Front coalition of rebels.

It is believed to have between 10,000 and 20,000 fighters and espouses a conservative ideology, though it has not expressed the same transnational aspirations as Al-Nusra or the IS group.

But many of its top leaders have ties to Al-Qaeda and the group has fought alongside Al-Nusra against other moderate rebel groupings in parts of northern Syria.

The reported raids are a new blow for Ahrar, which saw 47 members of its leadership killed in a blast in Idlib province in the northwest last month.

No group claimed responsibility for the attack, which wiped out most of Ahrar's senior religious and military chiefs, and it did not point the finger at anyone.

US and Arab nations have been carrying out air strikes against IS in Syria since 23 September in a bid to prevent the militant 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 IS since, but this second attack comes after Al-Nusra made gains against Western-backed rebel fighters in the 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 groups including Nusra and IS, as well as the forces of Syrian President Bashar al-Assad.

Elsewhere in the country, meanwhile, the coalition continued its strikes against IS, carrying out three raids against its positions in Tal Abyad on the Turkish border, the Observatory said.