HASAKEH: Fighting raged for a third day on Saturday between the militant Islamic State group and Kurdish forces in Syria after IS attacked a prison housing jihadists, with the violence killing nearly 90 people, a monitor said.

The assault on Ghwayran prison in the northeastern city of Hasakeh is one of IS’s most significant since its “caliphate” was declared defeated in Syria nearly three years ago.

“At least 28 members of the Kurdish security forces, five civilians and 56 members of IS have been killed” in the violence, said Rami Abdel Rahman, head of the Syrian Observatory for Human Rights.

IS launched the attack on Thursday night against the prison housing at least 3,500 suspected members of the jihadist group, including some of its leaders, the Observatory said.

The jihadists “seized weapons they found” in the detention centre and freed several fellow IS fighters, said the Britain-based monitor, which relies on sources inside war-torn Syria for its information.

Hundreds of jihadist inmates had since been recaptured but dozens were still believed to be on the run, it added.

With air support from the US-led coalition, Kurdish security forces have encircled the prison and are battling to retake full control of surrounding neighbourhoods, which jihadists have used as a launchpad for their attacks.

The Kurdish-dominated Syrian Democratic Forces (SDF) said “fierce clashes” broke out in neighbourhoods north of Ghwayran, where it carried out raids and killed more than 20 IS fighters.