Hasakeh, Syria: The death toll from fighting between US-backed Kurdish forces and Islamic State group who attacked a prison in northeast Syria four days ago reached 136 Sunday, a war monitor said. More than 100 insurgents late Thursday attacked the Kurdish-run Ghwayran jail in Hasakeh city to free fellow militants, in IS’ most significant military operation since its self-declared caliphate was defeated in Syria nearly three years ago. Intense fighting both inside and outside the jail saw the militants free detainees and seize stored weapons, according to the Britain-based Syrian Observatory for Human Rights, in what experts see as a bold IS attempt to regroup. And while the ferocity and expanse of the battle diminished late Sunday, concerns mounted about the fate of hundreds of children inside the prison, where the militants were holding out. “At least 84 IS members and 45 Kurdish fighters, including internal security forces, prison guards and counter-terrorism forces, have been killed” since the start of the attack, the Observatory said. Seven civilians have also died in the fighting in the city, the largest in northeastern Syria and controlled by a semi-autonomous Kurdish administration, it added. Helped by US-led coalition air strikes, the largely Kurdish Syrian Democratic Forces said Sunday they had sealed off the area around the jail and that “IS fighters located within the gates of the prison can no longer escape”. The coalition said that “the SDF have contained the threat,” while the Observatory reported that the intensity of fighting had died down. But the militants were holed up in a prison dormitory housing hundreds of detained children with suspected links to IS, the SDF said in a later statement. Inmates under the age of 18 were being used as “human shields,” to stymie advances against the militants, it said, adding that it would hold “the terrorists accountable if the children are hurt.” UNICEF, the UN’s agency for children, on Sunday called for the protection of 850 minors detained in Ghwayran. “As fighting continues, the risk for children increases, including to be harmed or forcibly recruited,” it said. The battles triggered a civilian exodus from areas around the prison. Kurdish authorities say thousands of people have fled in the harsh winter cold. IS fighters entered “homes… killing people,” said a civilian in his thirties who fled on foot on Sunday. “It was a miracle that we made it out,” he told AFP, carrying an infant wrapped in a wool blanket. Hamsha Sweidan, 80, a resident who had been trapped near the jail, said civilians were left without bread or water as the battle raged. “We have been dying of hunger and of thirst,” she said, adding that she had no idea where to go. IS has carried out regular attacks against Kurdish and Syrian government targets in the country since the rump of its once-sprawling proto-state was overrun in March 2019. Most of their guerrilla attacks have been against military targets and oil installations in remote areas, but the Hasakeh prison break could mark a new phase in their resurgence, in a country rife with insurgent groups after more than a decade of civil war.