The Kurdish-led Syrian Democratic Forces say they are mounting their “final assault” on Raqqa, the central position of the Islamic State in Syria.

Over the weekend, the US-supported SDF allowed a convoy of ISIS fighters and their families to leave the city, with only a remnant of about 200 to 300 diehards in less than 10% of Raqqa.

“The battle will continue until the whole city is clean,” an SDF statement said. The Baghdad-based spokesman for the US-led coalition, Ryan Dillon, said, “We still expect there to be difficult fighting.”

The SDF’s Talal Selo said about 275 ISIS personnel and family members departed. The Kurdish local council put out conflicting statements throughout Sunday over whether foreign fighters were in the convoy. Dillon said that the convoy was being convoys and that fighers had left biometric information.

The Islamic State also agreed to let remaining civilians depart.

Dillon said of the SDF-ISIS evacuation deal: “We may not always fully agree with our partners at times. But we have to respect their solutions.”

ISIS has controlled the city since late 2013, but has been pushed back across northern Syria by a combination of assaults by the SDF, by pro-Assad forces, and by Turkish-backed rebels. The SDF began moving across Raqqa Province early this year, and entered the city in early June.

During the operations, hundreds of civilians have been killed by the supporting US shelling and airstrikes.