Reports from Syria say thousands of US-backed fighters have launched an offensive to retake a crucial swathe of land near the Turkish border from ISIL.
The US says mostly Syrian Arab fighters are involved in the battle for the Manbij Pocket, with American special forces advisors away from the frontline. The operation could take weeks to complete.
It aims to choke off ISIL’s access to Syrian territory along the Turkish border that militants have long used as a logistics base for moving foreign fighters back and forth to Europe.
“It’s significant in that it’s their last remaining funnel” to Europe, a US military official said.
Contradicting the US description of those involved in the attempted recapture, the Syrian Observatory for Human Rights monitoring group says that mainly Kurdish YPG militia are taking part.
It says US-led air strikes in the area have killed 15 civilians.
Turkey considers the Syrian Kurdish YPG fighters to be terrorists and has been enraged by US backing for the militia in its battle with ISIL in Syria.
Separately, the Turkish military says it has shelled ISIL targets north of Aleppo in Syria, killing 14 militants.
NATO member Turkey is a member of the US-led coalition fighting ISIL in Syria and Iraq.