Battle in Syria between ISIS and Kurdish forces kills more than 120

Militants force mass jail break and civilians 'left without bread and water' as fighting rages

Syria Democratic Forces counter an ISIS siege of Ghwayran jail where a number of prisoners were broken out by the insurgents. EPA

A fierce battle was raging in Syria for a fourth day on Sunday between US-backed Kurdish forces and ISIS fighters who attacked a prison, killing at least 120 people including seven civilians, a war monitor said.

More than 100 insurgents attacked the Kurdish-run Ghwayran jail in Hassakeh to free extremists on Thursday, in the biggest ISIS operation since its self-declared caliphate was defeated in Syria nearly three years ago.

Militants freed detainees and seized weapons stored at the jail amid intense fighting, the Syrian Observatory for Human Rights said, in what experts regard as a bold ISIS attempt to regroup.

Kurdish security forces were on high alert in the northern Syrian city of Hassakeh as fighting with ISIS continued. AFP

"At least 77 ISIS members and 39 Kurdish fighters, including internal security forces, prison guards and counterterrorism forces, have been killed", inside and outside the prison, the Observatory said.

At least seven civilians are among those killed in the fighting, said the monitor.

Battles continued for a fourth consecutive day on Sunday as the Kurdish-led Syrian Democratic Forces, backed by coalition strikes, closed in on extremist targets.

"Fierce clashes broke out overnight on Sunday ... as part of an ongoing attempt by Kurdish forces to restore control over the prison and neutralise IS fighters deployed in surrounding areas," said the Observatory, which relies on a network of sources inside Syria.

An AFP correspondent in the city's Ghwayran neighbourhood reported the sound of heavy clashes in areas immediately surrounding the jail, which houses at least 3,500 suspected ISIS members.

The SDF was stationed in areas around the prison where they carried out combing operations and used loudspeakers to call on civilians to leave the area, the correspondent said.

ISIS fighters "are entering homes and killing people", said one civilian in his 30s who was fleeing on foot.

"It was a miracle that we made it out," he told AFP, carrying a young child wrapped in a wool blanket.

"The situation is still very bad. After four days, violent clashes are still ongoing."

Hamsha Sweidan, 80, who had been trapped in her neighbourhood 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 told AFP as she crossed into SDF-held areas in Hassakeh. "Now, we don't know where to go."

ISIS has carried out regular attacks against Kurdish and government targets in Syria since most of its once-sprawling proto-state was overrun in March 2019.

Most of its guerrilla attacks have been against military targets and oil installations in remote areas but the Hassakeh prison break could mark a new phase in the group's resurgence.

The Observatory said that Kurdish forces had managed to recapture more than 100 ISIS prisoners who had tried to escape but that many more were still on the run. Their exact numbers remained unclear.

In a statement released on its Amaq news agency overnight, ISIS claimed it took over a weapons storage room in the prison and freed hundreds of militants since the operation began with a double suicide bombing.

Syrian families flee their homes in the Ghwayran neighbourhood of Hassakeh, near the jail where ISIS freed a number of insurgent prisoners. AFP

Footage released on Amaq purported to show ISIS fighters carrying the group's black flag as they launched the attack on the jail and surrounded what appears to be a group of prison guards.

Another video released Saturday showed about 25 men whom ISIS said it had abducted as part of the attack, including some dressed in military fatigues.

AFP could not verify the authenticity of the footage.

Commenting on the video, the SDF said the captives were "kitchen staff" from the jail.

"Our forces lost contact with them during the first attack," it said.

Kurdish authorities have long warned they do not have the capacity to hold, let alone put on trial, the thousands of ISIS fighters captured in years of operations.

The say more than 50 nationalities are represented in a number of Kurdish-run prisons, where more than 12,000 ISIS suspects are being held.

Many of the ISIS prisoners' countries of origins have been reluctant to repatriate them, fearing a public backlash at home.