This photo provided by the Kurdish-led Syrian Democratic Forces shows fighters from the Kurdish-led Syrian Democratic Forces gathered around a body of an Islamic State group gunman who was killed after they attacked Gweiran Prison, in Hassakeh, northeast Syria, on Jan 21, 2022. (KURDISH-LED SYRIAN DEMOCRATIC FORCES VIA AP)

AMMAN - Kurdish-led Syrian Democratic Forces (SDF) troops aided by US troops tightened their siege of a prison housing Islamic State suspects after inmates took over the facility, residents and officials said on Sunday.

Dozens of inmates were killed in the attack on the prison in northeastern Syria, which began on Thursday. Militants detonated a car bomb near the prison gates, helping dozens of inmates flee to the neighbouring Ghweiran district of al-Hasaka, witnesses and officials said.

The SDF initially said it had thwarted the breakout and arrested 89 militants sheltering nearby, but later acknowledged that inmates had taken over parts of the facility.

Dozens of inmates were killed in the attack on the prison in northeastern Syria, which began on Thursday. Militants detonated a car bomb near the prison gates, helping dozens of inmates flee to the neighbouring Ghweiran district of al-Hasaka, witnesses and officials said

It said on Sunday the death toll of its fighters rose to 27 with over 160 of the attackers alongside 15 inmates killed in the deadliest rioting in detention centres holding thousands of suspected militants arrested after they were defeated with US support in north and east Syria.

The Pentagon confirmed the US-led coalition had carried out air strikes in support of the SDF as it sought to end the prison break.

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"The groups responsible for this brazen attack are now ultimately weaker," Maj. Gen. John W. Brennan, Jr., commander, Combined Joint Task Force, Operation Inherent Resolve said in a tweet.

Arab tribal figures in touch with residents in the area said US coalition troops had taken over positions around the prison and planes were seen flying overhead.

It was not clear how many inmates were in the prison, the biggest facility where the SDF has kept thousands of detainees. The relatives of many inmates say they are young children and others arrested on flimsy charges or for resisting the SDF's forced conscription.

Most Arab inmates have been held without charges or trial, fueling resentment by tribal members who accuse the Kurdish forces of racial discrimination, a charged denied by the Kurdish led forces.

The US-based Human Rights Watch says the SDF holds about 12,000 men and boys suspected of Islamic State affiliation, including 2,000 to 4,000 foreigners from almost 50 countries.

It was not clear how many inmates were in the prison, the biggest facility where the SDF has kept thousands of detainees. The relatives of many inmates say they are young children and others arrested on flimsy charges or for resisting the SDF's forced conscription

Thousands of others are held in secret detention centres where torture is rife, civic groups say. The Syrian Kurdish forces deny the accusations.

The United Nations children's agency (UNICEF) called for the release of nearly 850 children in the prison where it said their safety was at "immediate serious risk."

"We call for the release of children from prison. Detention of children should only be a measure of last resort and for the shortest time possible," Bo Viktor Nylund, UNICEF Syria Representative, said in a statement.

The inmates are held in overcrowded prisons where conditions are inhumane in many cases, according to Human Rights Watch and other rights groups.

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Many Arabs, who form a majority of the inhabitants of the areas under the control of the Syrian Kurdish YPG militia, accuse the Kurds of forcible conscription of youths and discriminationin jobs, an allegation rejected by Kurdish officials.

Local elders say support for Islamic State, which has resorted to guerrilla attacks since losing its last significant piece of territory in Syria in 2019, has grown with rising local resentment against the Kurdish-led rule.