The U.S.-led military coalition that's supposed to be bombing ISIS in Iraq and Syria accidentally hit a group of allied fighters instead.
18 members of the Syrian Democratic Forces, a rebel group backed by the U.S., were killed in a coalition airstrike near the ISIS stronghold of Raqqa.
The Pentagon says the site was misidentified by partner forces as an ISIS position and extended its "deepest condolences" to the SDF
The fight against ISIS has seen a recent spike in collateral damage from airstrikes. The military is still investigating another strike near Raqqa last month, which might have killed at least 30 civilians.