Civilian casualties were reported before as a result of US-led strikes on the last Islamic State (IS)-held areas.
The United States has been backing the Kurdish-led Syrian Democratic Forces to defeat the IS on the eastern bank of the Euphrates River near the Iraqi border. Airstrikes on this area have recently been renewed as the Kurdish-led groups were planning a second wave of attacks on the IS after a failed attempt on Sept. 10.
The Syrian government has long questioned the intention of the US-led operations in this oil-rich area.