Kurdish security forces amid the ongoing fighting with Daesh in Hasakeh on Saturday. AFP

Fighting raged for a third day between the Daesh group and Kurdish forces in Syria after Daesh attacked a prison housing militants, with the violence killing nearly 90 people, a monitor said.

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

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

Kurdish security forces deployed in Syria's northern city of Hasakeh on Saturday. AFP

Daesh launched the attack late Thursday against the prison, which houses at least 3,500 suspected members of the militant group, including some of its leaders, the Observatory said.

The militants seized weapons and freed several fellow Daesh fighters, said the Britain-based monitor, which relies on sources inside war-torn Syria.

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

Syrians flee their homes in the Ghwayran neighbourhood in the northern city of Hasakeh on Saturday. AFP

With air support from the US-led coalition, Kurdish security forces have encircled the prison and are battling to control surrounding neighbourhoods, which militants 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 Daesh fighters.

An AFP correspondent saw Kurdish fighters raiding homes near the jail in search of militants while coalition helicopters flew overhead.

In one location, Kurdish fighters gathered around five bloodied corpses of suspected Daesh fighters along a roadside, the correspondent said.

A Syrian family pictured while fleeing the Ghwayran neighbourhood in Hasakeh. AFP

The United States condemned the Daesh attack, praised the SDF's response and noted that Daesh fighters have been trying to free militant prisoners for more than a year.

"It is a credit to the diligent, capable efforts of the SDF and Global Coalition to Defeat ISIS Forces that they were able to thwart numerous attacks during that period and limit the severity of this one," State Department spokesman Ned Price said in a statement, using another acronym for Daesh.