ATMEH, Syria — US special forces carried out what the Pentagon said was a successful, large-scale counterterrorism raid in northwestern Syria early Thursday. First responders at the scene reported 13 people had been killed, including six children and four women.

The operation, which residents say lasted about two hours, jolted the sleepy village of Atmeh near the Turkish border — an area dotted with camps for internally displaced people from Syria’s civil war. The target of the raid was not immediately clear.

Pentagon press secretary John Kirby said in a brief statement that the mission was a success. “There were no U.S. casualties. More information will be provided as it becomes available.”

Several residents told The Associated Press they saw body parts scattered near the site of the raid, a house in Syria’s rebel-held Idlib province. They spoke on condition of anonymity for fear of reprisals, and said the raid involved helicopters, explosions and machine-gun fire.

It was the largest raid in the province since the 2019 U.S. assault targeting the Islamic State leader Abu Bakr al-Baghdadi. Idlib is is broadly controlled by Turkey-backed fighters, but is also an Al-Qaida stronghold and home to several of its top operatives. Other militants have also found refuge in the region.

Reports on the number of dead varied. A journalist on assignment for the AP saw body parts around the house, whose upper story was almost completely leveled leaving rubble in the surrounding olive grove.

Blood could be seen on the walls and floor of the remaining structure, which contained a wrecked bedroom with a child’s wooden crib on the floor. On one damaged wall, a blue plastic swing for children was still hanging. The kitchen was blackened with fire damage.

The opposition-run Syrian Civil Defense, first responders also known as the White Helmets, said 13 people were killed in shelling and clashes that ensued after U.S. the commando raid. They included six children and four women, it said.

The Britain-based Syrian Observatory for Human Rights, an opposition war monitor, also said the strike killed 13 people, including four children and two women. Ahmad Rahhal, a citizen journalist who visited the site, reported seeing 12 bodies.

The Pentagon provided no details on who was the target of the raid, or if any combatants or civilians on the ground were killed or injured.

Residents and activists described witnessing a large ground assault, with U.S. forces using loudspeakers urging women and children to leave the area.

There was at least one major explosion. A U.S. official said that one of the helicopters in the raid suffered a mechanical problem and had to be blown up on the ground. The U.S. official spoke on condition of anonymity to discuss details of the military operation.

The Observatory said troops for the U.S.-led coalition using helicopters landed in the area and attacked a house. It said the force clashed with fighters on the ground. Taher al-Omar, an Idlib-based activist, also said he witnessed clashes between fighters and the U.S. force.

The military operation got attention on social media, with tweets from the region describing helicopters firing around the building near Atmeh. Flight-tracking data also suggested that multiple drones were circling the city of Sarmada and the village of Salwah, just north of the raid’s location.

The clandestine operation came as the Islamic State group was reasserting itself, carrying out some of its biggest attacks since it was defeated in 2019. In recent weeks and months, the group has launched a series of operations in the region, including a 10-day assault late last month to seize a prison in northeastern Syria.

A U.S.-backed Kurdish-led force said more than 120 of their fighters and prison workers died in the effort to thwart the IS plot, whose goal appeared to free senior IS operatives from the prison. The prison houses at least 3,000 Islamic State group detainees.

The attempted prison break was the biggest military operation by the extremist group since IS was defeated and members scattered to havens in 2019. The U.S.-led coalition carried out airstrikes and deployed American personnel in Bradley Fighting Vehicles to the prison area to help the Kurdish forces.

At a news conference Monday, an SDF senior official Nowruz Ahmad said the prison assault was part of a broader plot that IS had been preparing for a long time, including attacks on other neighborhoods in Hassakeh, Shaddada and areas of Deir el-Zour in eastern Syria and on the al-Hol camp in the south, which houses thousands of families of IS members.

The U.S.-led coalition has targeted high-profile militants on several occasions in recent years, aiming to disrupt what U.S. officials say is a secretive cell known as the Khorasan group that is planning external attacks. A U.S. airstrike killed al-Qaida’s second in command, former bin Laden aide Abu al-Kheir al-Masri, in Syria earlier this year.