BAGHDAD - Fighting raged for a second day in northeastern Syria, following what authorities described as a foiled plot by Islamic State terror group sleeper cells to break their captured comrades out of prison.

The U.S.-backed Syrian Democratic Forces said IS sleeper cells launched the attack late Thursday, detonating a car bomb outside the al-Sina'a prison, in the Geweran neighborhood of Hasakah, before clashing with security forces.

Fighting quickly spread into surrounding areas, while inside the prison, IS detainees began burning blankets and other materials.

SDF officials said reinforcements were brought in to help quell the fighting, and an official with the U.S.-led anti-IS collation said coalition aircraft have taken to the skies above the prison and the surrounding neighborhoods to support SDF efforts.

This photo provided by the Kurdish-led Syrian Democratic Forces shows a flag and bags of Islamic State group fighters arrested by the Kurdish-led Syrian Democratic Forces after they attacked Gweiran Prison, in Hassakeh, northeast Syria, Jan. 21, 2022.

A SDF spokesman, Farhad Shami, posted on social media Thursday the prison break had been thwarted and that the attackers had 'fled to the al-Zohour neighborhood near the prison and hid in civilian homes.'

But the fighting continued through midday Friday, with reports that some IS prisoners did manage to escape.

Local security forces and the SDF told VOA Friday at least 120 prisoners had been recaptured.

The SDF further said seven prisoners were killed by IS operatives when they tried to surrender.

This photo provided by the Kurdish-led Syrian Democratic Forces shows some Islamic State group fighters, who were arrested by the Kurdish-led Syrian Democratic Forces after they attacked Gweiran Prison, in Hassakeh, northeast Syria, Jan. 21, 2022.

SDF officials also said at least five IS fighters have been killed in the ongoing fighting, including one fighter of 'Chinese nationality.'

IS Friday issued a statement claiming responsibility for the attack on the al-Sina'a prison.

The claim, published by the terror group's Amaq news agency, described the operation as 'a broad offensive,' according to a translation by the SITE Intelligence Group, and that its fighters were continuing to battle with U.S.-backed forces.

Thursday's attack by IS sleeper cells is not the terror group's first attempt to free some of an estimated 5,000 fighters held in SDF-run prisons in and around Hasakah.

The SDF said it foiled an earlier prison break plot this past November, which sparked a series of reprisals by IS cells.

IS Cells in NE Syria Retaliate for Foiled Prison-Break Plot

Further complicating the situation on the ground, the Syrian-based People's Protection Units (YPG), an offshoot of the Turkey-based Kurdistan Workers' Party (PKK), claimed on social media that Turkish drones had attacked convoys sent to aid SDF forces with the fighting in Hasakah.

The U.S. has labeled the PKK as a terrorist organization, and Ankara maintains the SDF, despite U.S.-backing, is linked to both the PKK and YPG.

VOA has not been able to independently confirm the YPG's claims. Neither the Turkish Embassy in Washington nor U.S. Central Command, which oversees U.S. forces in the region, have yet to respond to requests for comment.

Since declaring the military defeat of IS in March 2019, the SDF has been holding more than 10,000 IS fighters, including about 2,000 foreign nationals.

The United States and other coalition countries have sent money and material to the SDF to help maintain the prisons, but efforts to repatriate many of the foreign nationals have failed.

U.S. intelligence analysts say IS still in control of about 10,000 fighters across Syria and Iraq.

Estimates by the U.S.-based Counter Extremism Project said IS carried out 37 attacks across northeastern Syria over the last three months of 2021.

The SDF said for all of 2021 it carried out 115 operations against IS cells, resulting in 802 arrests and the disruption of 47 plots said to be in their final stages of planning.