The US-backed force waging the battle against ISIS in its last pocket has killed dozens of fighters and captured an arms dump as it restarted an offensive to wrest the scrap of territory from the group. The advances in Baghouz by the Syrian Democratic Forces (SDF), a Kurdish-Arab coalition of fighters, have been slow as they are facing a major threat from militants hidden in underground tunnels, as well as booby-traps laid by the group’s remaining diehards. Four ISIS fighters attempted suicide attacks and one SDF fighter was killed and four were wounded during the clashes, said Mustafa Bali, an SDF spokesman, on Twitter. The fighting came a day after an SDF official said they could soon resume the offensive against ISIS, adding that the battle could last three days. SDF official Aras Orkesh said on Saturday that about 2,500 Kurdish and Arab fighters are ready for the battle in and around the eastern Syrian village, where ISIS fighters still have a presence. The battle opened on Sunday evening with large explosions and mushroom clouds rising into the air over Baghouz, on the Euphrates River in eastern Syria, as the Syrian Democratic Forces battered the village with artillery and gunfire, hitting an ISIS ammunition dump. On Monday, at least one airstrike was carried out and renewed artillery and heavy gunfire rained down on the encampment. Some 500 ISIS fighters are believed to be still in the territory, along with possibly 3,000 to 4,000 civilians, including women and children, mainly family members who remained after thousands of civilians streamed out of Baghouz in past week during pauses in the fighting. The battle was expected to be over in days but those estimates have now been extended to weeks. The SDF has been cautious to try and do all it can to remove civilians from inside the encampment before a major offensive is launched. The US-backed force is demining every open inch of land in Baghouz that it advances on. The group has laced the pocket with mines and peppered buildings with booby-traps, making liberating the area a much more perilous task. The SDF fighters also face the threat of sniper fire, so are moving at a slow pace to avoid casualties. The defeat of ISIS at Baghouz will mark a milestone in the campaign against the militant group, ending its control of populated territory in the area straddling Iraq and Syria where it suddenly expanded in 2014 and declared a caliphate. However, it has already shown it will continue to mount a potent security threat, with a string of insurgent attacks in both countries. Early estimates suggested that just 5,000 people were in Baghouz before the SDF offensive began last month. But tens of thousands have poured out of the area, swelling displacement camps such as Al Hol in Deir Ezzor province, where rights groups say basic services are on the brink of collapse. Included in those fleeing the area are Yazidi men and women who have been held hostage by the militant group for years. There is also speculation that some Western nationals could be captive inside Baghouz, but this remains unconfirmed. Despite its losses, ISIS has still claimed a series of attacks against SDF forces and coalition forces in eastern Syria.