BEIRUT (Reuters) – U.S.-backed forces battling Islamic State near the Turkish border in northern Syria said on Friday they had launched a final assault to flush the remaining jihadists out of the city of Manbij.

The Syria Democratic Forces (SDF), with air support from a U.S.-led coalition, said last week they had taken almost complete control of Manbij, where a small number of IS fighters had been holed up.

The SDF’s offensive, which began at the end of May, aims to remove Islamic State from areas it controls along the Turkish border, which was for years a route through which the group moved fighters and weapons.

The SDF said it was now conducting a final sweep of the city before they officially announce the operation is complete.

Friday’s attack is “the last operation and the last assault,” said Sharfan Darwish, a spokesman for the Syrian Arab and Kurdish forces.

Darwish said roughly 100 Islamic State fighters were left in the center of the city, and that they were using civilians as human shields. Several civilians were killed trying to flee, he said.

Reuters pictures showed residents being released from an Islamic State-held neighborhood on Friday and being welcomed by SDF forces.

The Syrian Observatory for Human Rights, which monitors Syria’s five-year conflict, later said around 500 cars had left Manbij carrying Islamic State members and civilians. They were heading northeast toward Jarablus, a town under Islamic State control on the Turkish border, the Observatory said.

The convoy carried the final Islamic State members leaving the city, under an agreement between the fighting parties that would not be announced officially, the Observatory said, marking the end of the operation.

The SDF could not immediately be reached for comment on that report.

The SDF’s campaign quickly captured the countryside surrounding Manbij, but slowed once fighting entered the city. The SDF said it had been avoiding a large-scale assault inside Manbij out of concern for civilians.

Dozens of people were killed in suspected U.S. coalition air strikes last month, residents and monitors said.

(Reporting by Suleiman al-Khalidi, John Davison and Lisa Barrington; Editing by Larry King and Robin Pomeroy)