Kurdish-led forces on Thursday found dozens of jihadists holed up in a Syrian prison as they carried out mop-up operations after recapturing the facility from Islamic State group jihadists.

An IS assault on the sprawling Ghwayran prison complex near the city of Hasakeh on January 20 sparked six days of fighting, in violence that claimed more than 200 lives.

It was the most high-profile attack launched by the jihadists since the loss of their “caliphate” nearly three years ago.

The Kurdish-led Syrian Democratic Forces said they had retaken full control of Ghwayran prison on Wednesday, ending battles that turned the largest city in northeastern Syria into a war zone.

But search operations the next day found around 60-90 jihadists still holed up in one wing of the prison, the SDF said, adding that 3,500 IS inmates had so far surrendered to its forces.

The Syrian Observatory for Human Rights said Kurdish forces are combing areas inside the prison, proceeding with “great caution over fears of suicide bombers or landmines laid by the IS”.