Despite losing most of the territory they once held, Islamic State (IS) fighters are now holding their ground against U.S.-backed forces in their last stronghold in eastern Syria.
Fierce clashes have been taking place around Hajin, in the Syrian province of Deir el-Zour, for three weeks, with Syrian Democratic Forces (SDF) trying to close in on the remaining IS militants in the town.
But local sources say IS fighters have been putting up a tough fight in Hajin, taking advantage of foul weather.
"In the last 24 hours, the SDF has brought additional reinforcements to add more pressure on [IS] fighters in the area," Rami Abdulrahman, director of the U.K.-based Syrian Observatory for Human Rights, told VOA.
Abdulrahman added that several hundred local tribal fighters had joined forces with the SDF to combat IS.
The “al-Shaitat tribe, which is one of the largest Arab tribes in Deir el-Zour, has shown determination to battle [IS] militants," Abdulrahman said.
Tribe members slain
In 2015, IS killed nearly 700 male members of the al-Shaitat tribe because they refused to pledge allegiance to the terror group. Ever since, tribe members have been seeking revenge against IS.
In late November, at least 50 SDF fighters were reportedly killed after IS militants counterattacked two villages in Deir el-Zour that recently had been liberated from the group.
"This is the last bastion for IS in all of Syria, and so to them this battle is a life-or-death matter," Sadradeen Kinno, a Syrian reporter who closely follows IS activities in the region, told VOA. “Their so-called caliphate will literally be obliterated when Hajin has been captured. So that's why we see most of IS's fighting force is now present in this part of Deir el-Zour."
With help from the U.S.-led coalition, the Kurdish-led SDF has made major advances against IS, liberating large swaths of territory from the extremist group, including its de facto capital, Raqqa.
The SDF now controls approximately one-third of Syria, making it the second-largest entity in the war-torn country, after the Syrian regime troops.
But analysts say in Hajin, IS has reportedly mixed with civilians, using them as human shields and hampering the progress of anti-IS forces.
"It's really hard for the SDF and U.S.-led coalition to carry out a full-blown operation inside the city. The coalition is already in hot water for reports of civilian deaths in Deir el-Zour," Kinno said.
Anti-IS coalition officials have denied that U.S. or allied warplanes were responsible for airstrikes that reportedly killed about 60 civilians in eastern Syria, including Hajin, in mid-November.
But British Maj. Gen. Christopher Ghika, deputy commander for strategy and information for the U.S.-led coalition, said that coalition leaders were looking into reports that coalition actions caused civilian causalities.
"We will investigate them, as we investigate every allegation of civilian casualties," Ghika told reporters in November.
Analysts say that recapturing Hajin and surrounding territory held by IS could take longer than expected.
"The long-term trend here is that Hajin will eventually be retaken from IS," said Aymenn Jawad al-Tamimi, a researcher at the Middle East Forum, a U.S.-based think tank.
He assessed that if and when it has been cleared from eastern Syria, IS would re-emerge "as an insurgent movement. I don't think they will substantially regain territory, though."
Located on the eastern bank of the Euphrates River, Hajin offers IS fighters access to Syrian regime-held areas on the western side of the river.
Last week, the terror group posted photos on social media that purportedly showed the militants using boats to move between the two sides of the river.
"IS fighters manage to use the river to move and to get supplies from regime-held areas toward the desert," reporter Kinno said.
IS "has built a massive network in the desert — mostly ungoverned territory — and has access to weapons and other supplies," he added.
Syrian regime troops and Iranian-backed Shiite militias continue a separate campaign against IS in eastern Syria. But they are also at odds with the U.S.-backed SDF.
"I think [IS fighters] exploit problems in security created by the fact [that] control is divided between two sides that don't really coordinate," analyst al-Tamimi said.