Opposition activists say airstrikes have hit several positions of the Islamic State group in its de facto capital of Raqqa in northern Syria.

The Britain-based Syrian Observatory for Human Rights says 15 blasts shook the northern and eastern outskirts of Raqqa on Sunday, killing 32 ISIS fighters and wounding more than 40.

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. It had no word on casualties.

RBSS did not say which country carried out the airstrikes while the Observatory said they are believed to be from the U.S.-led coalition that began targeting ISIS in Syria in September 2014.

Russia and a U.S.-led coalition that includes France have been pounding Raqqa.