BAGHDAD — U.S.-backed Syrian Kurdish forces said Monday they regained control of a portion of a prison in northeast Syria that Islamic State militants held after Friday’s attack, but hundreds of boys are still being held hostage.
The prison holds about 3,000 suspected ISIS fighters, as well as nearly 700 boys who are used as human shields by ISIS.
A paramilitary spokesman said ISIS was threatening to kill the boys if the US and Kurdish-led forces continued their assault on the prison.
Hundreds of Islamic State fighters attacked the makeshift prison on Friday in an attempt to free their detained comrades in one of the group’s most daring attacks in the region since the fall of the so-called caliphate three years ago.
Kurdish forces, the Syrian Democratic Forces, said they recaptured one of the three prison buildings during Monday’s dawn raid and that about 300 Islamic State fighters have surrendered, but the detained boys are still at risk.
The Rojava Information Center, run by pro-Syrian Kurdish activists, said part of the complex is still under ISIS control.
“We have reports that ISIS is threatening to kill all minors if we continue to attack them,” said Farhad Shami, an SDF spokesman. He estimated that 25 percent of the complex was still under ISIS control.
The United States has launched airstrikes from Apache helicopters over the past three days to try to break the siege, killing an unknown number of prisoners.
Mr. Shami said that 30 SDF fighters had been killed in the operation to liberate the prison, and that about 200 ISIS fighters and prisoners who had joined them in their attempt to escape had been killed in the operation since Friday.
Among the prisoners are boys as young as 12, including Syrians, Iraqis and about 150 non-Arab foreigners. Some were transferred to prison when they were deemed too old to remain in detention camps that housed the families of Islamic State suspects.
The siege of the Gweran prison in Hasaka demonstrated that the Islamic State is still capable of conducting a coordinated military operation despite its territorial defeat by the United States and international forces three years ago. At its peak, the jihadist group held an area the size of Great Britain spanning Iraq and Syria.
Syrian Democratic Forces commander Mazloum Kobani said ISIS had mobilized sleeper cells and used suicide bombers to organize the escape.
The SDF have complained for years that they were unable to safely manage the prison where ISIS fighters were held after they were defeated from a battlefield in southeastern Syria three years ago. The prisoners hail from dozens of countries, most of which refused to take them back.
Hwayda Saad contributed reporting from Beirut, Lebanon; and Sangar Khalil from Erbil, Iraq.