U.S.-led coalition aircraft were sent near the northeastern city of Hasaka, Syria to protect coalition ground forces in response to an earlier bombing by Syrian jets on August 18, a Pentagon official said on Friday.

On the other hand ISIS combatants have evacuated their families from a Syrian town at the Turkish border near a city that they recently lost to U.S.-backed militias, a monitor group reported on Friday, a sign they may be preparing to face an attack there.

Last week’s advance by the Syrian Democratic Forces (SDF) of Manbij, 40km to their south, has left ISIS fighters in Jarablus in danger of being cut off from the militant group’s main stronghold.

The town is located at the eastern edge of an ISIS stretch 55km along the Turkish border, and could be encircled by any SDF thrust northwards from its positions further to the west. SDF positions on the Euphrates already look directly across to Jarablus on the opposing bank.

More than 50 families of ISIS fighters and leaders arrived in the group’s stronghold of Raqqa from Jarablus and the larger town of al-Bab, between Manbij and Aleppo, the Syrian Observatory for Human Rights, a U.K.-based war monitor, said.

Separately, a senior Syrian rebel source told Reuters that ISIS was moving personnel out of Jarablus.
The SDF have not yet declared what their next target will be after capturing Manbij.

A successful advance north could cut ISIS ate off from the Turkish border, while a thrust west could threaten al-Bab, an important Islamic State stronghold.

After Manbij fell to the SDF, some local fighters announced they had established a military council for al-Bab, signaling they believed an assault on ISIS in the town would soon take place. The SDF denied having any links to the council.

The U.S.-backed SDF is made up of both Kurdish fighters, including the YPG militia, and local Arab armed groups. It has denied any links to a military council established last week