ATME, Syria – US special forces hunted down high-ranking jihadists in a rare airborne raid in northwestern Syria on Thursday, killing 13 people in an operation the Pentagon described as "successful".

The operation was thought to be the biggest of its kind by US forces in the jihadist-controlled Idlib region since the 2019 raid that killed Islamic State group leader Abu Bakr al-Baghdadi.

The targets of the latest operation around the town of Atme, which residents and other sources said lasted around two hours, were not immediately clear.

Names circulating on social media and among local residents suggested the US raid was not aimed at IS operatives but at members of rival jihadist group Al-Qaeda.

The Pentagon stopped short of revealing its target in the nighttime raid but said more information would be provided later.

"US Special Operations forces under the control of US Central Command conducted a counterterrorism mission this evening in northwest Syria," spokesman John Kirby said in a statement.

"The mission was successful. There were no US casualties," he added, without elaborating.

The Syrian Observatory for Human Rights said seven civilians were among at least 13 people killed in the operation, which saw elite US forces make a perilous helicopter landing near Atme.

"13 people at least were killed, among them four children and three women, during the operation," Observatory chief Rami Abdel Rahman told AFP.

AFP correspondents were able to visit a home on the outskirts of Atme which appeared to be one of the main targets of the US special forces.

- Fierce battle -

The two-storey building of raw cinder blocks bore the scars of an intense battle, with torn window frames, charred ceilings and a partly collapsed roof.

In some of the rooms, blood was splattered high on the walls and stained the floor, littered with foam mattresses and shards from smashed doors.

US special forces have carried out several operations against high-value jihadist targets in the Idlib area in recent months.

The area, the last enclave to actively oppose the government of Bashar al-Assad, is home to more than three million people and is dominated by jihadists.

The region is mostly administered by Hayat Tahrir al-Sham, a group led by former members of what was once Al-Qaeda's franchise in Syria.

In recent years, it has tried to cast itself as a more moderate player focused only on Syrian matters and condemning international terrorism.

HTS has carried out military sweep operations to weed out more radical jihadist groups, such as Hurras al-Deen, which has more organic links with Al-Qaeda.

Atme is home to a huge camp for families displaced by the decade-old conflict and which experts have warned was being used by jihadists as a place to hide among civilians.

On October 23, the US military announced the killing of senior Al-Qaeda leader Abdul Hamid Al-Matar.

"Al-Qaeda uses Syria as a safe haven to rebuild, coordinate with external affiliates, and plan external operations," said Central Command spokesman Army Major John Rigsbee in a statement at the time.

Syrian government forces and their main military backer Russia have carried out repeated attacks against jihadist and rebel groups in the Idlib region.

However a ceasefire deal which was brokered by Moscow and Ankara, the two main foreign powers in the area, almost two years ago is still officially in place.

Assad has long insisted his goal was to recapture the whole of Syria, including Idlib province, but the contours of the jihadist-run enclave have remained largely unchanged since early 2020.