Air strikes have hit several positions of the Islamic State group in its de facto capital of Raqqa in northern Syria.

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

A Raqqa-based activist group that reports on IS, known as Raqqa is Being Slaughtered Silently (RBSS), said warplanes struck IS positions on the edge of the city.

RBSS did not say which country carried out the air strikes while the Observatory said they are believed to be from the US-led coalition that began targeting IS in Syria in September 2014.

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

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