Syrian activists say an airstrike by the U.S.-led coalition has killed at least 20 civilians in a part of Syria held by the Islamic State group.

The Britain-based Syrian Observatory for Human Rights says 20 were killed and around 30 wounded in the strike on the village of Heisha early Wednesday. The village is north of the extremist group's de facto capital, Raqqa.

Raqqa is Being Slaughtered Silently, a local media collective, says 23 civilians were killed.

The coalition did not immediately respond to a request for comment.

It was not clear how the groups determined the coalition was behind the strike, but the international force is flying dozens of sorties in the region in support of a U.S.-backed push by Syrian Kurdish forces on Raqqa.