The US-led coalition against the Islamic State group hit a weapons depot belonging to a rebel group allied with Al-Qaeda's Syrian affiliate overnight in northwestern Syria, a monitor said Wednesday.

The strikes killed 10 members of the Jaish al-Sunna group, as well as a child, the Syrian Observatory for Human Rights said.

The raid hit the Atmeh region of Idlib province, home to a large camp for displaced Syrians, but did not strike the camp itself, Observatory director Rami Abdel Rahman said.

"The strikes hit the weapons depot, but there are civilians living nearby," he said.

Jaish al-Sunna belongs to the Army of Conquest alliance that has captured much of Idlib province from the Syrian government in recent months.

The Army of Conquest alliance includes Al-Nusra Front, which is Al-Qaeda's Syrian affiliate, as well as other Islamist rebel forces.

The US-led coalition fighting IS began strikes in Syria last September and has rarely expanded its targets beyond the jihadist group.

It has on occasion hit positions belonging to Al-Nusra, though Washington has identified those strikes as hitting what it calls the Khorasan group, which is says is a cell of senior Al-Qaeda leaders.

Early on in the air campaign, strikes also hit Ahrar al-Sham, another Islamist rebel group that is part of the Army of Conquest alliance.