The U.S.-led coalition has stepped up its aerial campaign on Raqqa city in support of Kurdish militias days before launching a major offensive to expel the Islamic State (ISIS) from the group's de facto capital in Syria.
Local monitoring group Raqqa is Being Slaughtered Silently said coalition warplanes have also dropped leaflets demanding civilians to flee the city.
ISIS news agency Amaq said Sunday that 17 civilians were killed in the U.S artillery bombardment.
On Saturday, U.S.-led airstrikes killed detainees held by ISIS in the town of Mansoura in the western Raqqa countryside.
The U.S.-backed Syrian Democratic Forces are just 2 miles from the first neighborhoods of Raqqa on the eastern side; such an advance followed a promise on Thursday that no harm would come to ISIS fighters in Raqqa who turned themselves in by the end of the month.
This article was edited by The Syrian Observer. Responsibility for the information and views set out in this article lies entirely with the author.