Air strikes by the US-led coalition Saturday killed 43 people, mostly civilians, in a holdout of the ISIS extremist group in eastern Syria, a Britain-based monitor said.
Seventeen children were among 36 ISIS family members killed in Abu Husn village of Deir Ezzor province near the Iraqi border, the Syrian Observatory for Human Rights said.
Another seven victims had not yet been identified as either civilians or ISIS fighters, it said.
The US-led coalition has been backing a Kurdish-Arab alliance called the Syrian Democratic Forces (SDF) fighting to expel the extremist from the pocket around Abu Husn.
“It’s the highest death toll in coalition air strikes since the SDF launched its attack against the ISIS pocket” in September, Observatory chief Rami Abdel Rahman said.
The coalition has repeatedly said it does its utmost to prevent civilian casualties.
“The avoidance of civilian casualties is our highest priority when conducting strikes against legitimate military targets with precision munitions,” spokesman Sean Ryan told AFP this week.
ISIS overran large swathes of Syria and neighboring Iraq in 2014, proclaiming a “caliphate” in land it controlled.
But the extremist group has since lost most of it to various offensives in both countries.
In Syria, the group has seen its presence reduced to parts of the vast Badia desert and the pocket in Deir Ezzor.
The coalition has since 2014 acknowledged direct responsibility for over 1,100 civilian deaths in Syria and Iraq, but rights groups put the number killed much higher.
In another military development, Russia has threatened the Syrian opposition forces after they failed to meet a deadline set up by Russian and Turkish troops to enforce a new demilitarized zone in the city of Idlib.
The buffer zone required the withdrawal and separation of extremists from moderate opposition forces.