BEIRUT — 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, a monitoring group said.

More than 15 explosions hit ISIS positions in the countryside of Raqqa province and near its capital, Raqqa city, the Britain-based Syrian Observatory for Human Rights said. Raqqa is ISIS' Syrian stronghold.

The coalition said it hit Raqqa and other areas of northern and eastern Syria on Sunday.

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.

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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.