The US-backed Syrian Democratic Forces (SDF) on Monday captured several positions inside Baghouz, the Islamic State’s last enclave on Syrian territory. The SDF launched its assault on the city over a week ago and officials last week claimed that ISIS was about to be defeated. However, the remaining ISIS fighters in the enclave have continued their final stance, which has slowed down the SDF campaign.

On Sunday, the SDF stated that over 60,000 people have left Baghouz since Jan. 9, including about 5,000 ISIS fighters who surrendered. SDF officials also admitted that they “are facing several difficulties regarding the operations,” including the presence of mines and other explosives that ISIS fighters have planted in the enclave, and the discovery of a vast network of tunnels under the city, used by ISIS fighters and their supporters.

Read more: US-backed force says it has taken positions in Islamic State Syria camp