The Syrian Democratic Forces have all but encircled Manbij, a key waypoint on an IS supply line between the Turkish border and the extremist group's de-facto capital, Raqqa, according to an SDF adviser.
Nasser Haj Mansour said the IS group was allowing families to flee the town to nearby Jarablus and al-Bab. Some civilians fled to liberated villages and to the advancing forces, the adviser told the AP by messaging service from his position near the front line. He estimated some 15,000 civilians had fled.
The Kurdish-led force, which also includes Arab fighters, has advanced under the cover of US-led airstrikes, and the US has embedded 300 Special Forces troops with it, though Washington says they are there in an advisory capacity.
Haj Mansour said IS militants were fighting to keep every village. "This is not something we have seen before. They are not leaving any positions," he said.
More From This Section
The Observatory, which relies on a network of local activists, said 82 fighters and 25 civilians were killed in the first week of fighting.
The SDF has said Manbij natives would fight the final campaign for the predominantly Arab town in an apparent bid to allay such fears.
The UN's children's agency UNICEF meanwhile said a hospital it supported along with two others in rebel-held parts of Aleppo came under attack today, as fighting in Syria's largest city intensified once again.
"The Al Hakim hospital, a UNICEF supported facility, is one of the few that still provide pediatric services" in the eastern parts of the divided city, said Peter Salama, the agency's regional director.