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, with the U.S.-led coalition sending in Apache attack helicopters and F-16 jets.
"We have provided some airstrikes to support them as they deal with this particular prison break," Pentagon press secretary John Kirby told reporters Friday, in response to a question from VOA.
Earlier, a coalition official speaking on the condition of anonymity due to the ongoing fighting told VOA that U.S. and coalition aircraft had been called in to respond to the IS attack, while another official described the attack as an "evolving situation."
SDF officials initially claimed the attempted prison break had been thwarted late Thursday. But reports of continued fighting persisted, and a spokesman later said some of the attackers had "fled to the al-Zohour neighborhood near the prison and hid in civilian homes."
SDF General Commander Mazloum Abdi on Friday said the initial attack had been repelled with coalition support, though he described the attack as a major operation.
"The terrorist ISIS organization has mobilized most of its sleeper cells in attempt to organize a jailbreak," Abdi said on Twitter. "We will not stop until all criminal elements are put behind bars."
There also were conflicting reports about whether any IS prisoners managed to escape.
Local security forces and the SDF told VOA on Friday more than 100 prisoners had been recaptured.
SDF spokesman Farhad Shami later posted video on social media, claiming to show some of the escaped prisoners, many half-naked and some wounded, being taken back into custody.
The SDF said seven prisoners were killed by IS operatives when they tried to surrender and that at least five IS fighters have been killed in the ongoing fighting, including one fighter of "Chinese nationality."
Officials said as of late Friday, at least 18 SDF soldiers had been killed, and that five civilians were also dead, some beheaded by IS fighters after they refused to allow them into their homes.
IS on 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 said that its fighters were continuing to battle with U.S.-backed forces.
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.
When asked about the claims, the Pentagon did not have any comment. But the British-based Syrian Observatory for Human Rights, a war-monitoring group, confirmed the attack Friday, saying that an armed drone believed to have been flown by Turkish forces struck a military vehicle on a highway north of Hasakah, injuring several SDF soldiers.
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.
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 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.
VOA Kurdish Service contributed to this report.