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. - AFP