At least 32 ISIS fighters were killed and 40 more wounded in Syria's Raqqa province on Sunday, in a series of air strikes believed to be carried out by a U.S.-led coalition targeting the jihadists, the Britain-based Syrian Observatory for Human Rights said.

More than 15 explosions hit ISIS positions in the countryside of Raqqa province and near its capital, Raqqa city, the Observatory reported. Raqqa is ISIS’ Syrian stronghold

A Raqqa-based activist group that reports on ISIS, known as Raqqa is Being Slaughtered Silently, said warplanes struck ISIS positions on the edge of the city. The group had no word on casualties.

A Facebook page used by ISIS supporters said the airstrikes were carried out by Russian warplanes on the outskirts of Raqqa and killed fifteen people, including eight children and five women. It said 25 people were wounded in the airstrikes.

In central Syria, at least 45 air strikes, probably carried out by Russia, hit the city of Palmyra, which is also under ISIS’ control, the Syrian Observatory for Human Rights said. Injuries were reported, but no details on the casualty toll were available.

The United States and its allies have been bombing ISIS in Iraq and Syria in an effort to drive the group from swathes of territory it controls in both countries.

Britain joined the effort this week after lawmakers approved bombing ISIS targets in Syria. Hours after the vote, British bombers struck oilfields the government says are being used to fund attacks on the West. They made a second round of strikes on Friday.

Russia is waging a separate air campaign in Syria, which it launched on September 30 in support of its ally President Bashar Assad. Russia has said its air campaign targets ISIS, but the West says most raids have hit other foreign-backed rebel groups.