U.S.-led coalition airstrikes in the Islamic State of Iraq and Syria’s de facto capital in Syria are killing hundreds of civilians each month.

At least 725 civilians have been killed in coalition airstrikes since the offensive to retake Raqqa began June 6, said Airwars, a London-based monitoring organization.

Lt. Gen. Stephen Townsend, the top U.S. commander in the country, said the Pentagon was aware of the reports.

The coalition has beefed up its team investigating claims of civilian casualties. More than 270,000 people have fled Raqqa since the offensive began. At least 18,000 are believed to be trapped in the city.