BEIRUT — Fighting against the Islamic State group in its last enclave in eastern Syria “is going very well,” a U.S. official said Saturday as U.S.-backed Syrian fighters battled the extremists on the edge of the largest urban area they still hold.

Spokesman for the U.S.-led Coalition Col. Sean Ryan’s comments came a day after the U.S.-backed Syrian Democratic Forces captured the town of Hajin, the largest urban area controlled by ISIS in the enclave.

Ryan said ISIS still poses a threat and its fighters are regrouping, planting improvised explosives devices to slow the progress of SDF offensives. He added that the “end days” of ISIS in the enclave they hold near Iraq’s border are getting closer, however, “they still have the capability for coordinated attacks, and the fight is not over.”

The Britain-based Syrian Observatory for Human Rights, a war monitor, said SDF fighters are removing explosives in Hajin and fortifying their positions amid fighting on the eastern outskirts of the town.

SDF has been trying to take the enclave since it launched an offensive on Sept. 10. Since then, 932 ISIS gunmen, 545 SDF fighters and scores of civilians have been killed in the area, according to the Observatory.

The SDF offensive intensified over the past days under the cover of airstrikes by the U.S.-led coalition.