The Syrian Democratic Forces (SDF) stressed they would freeze operations if Turkey attacked, as widely expected after a pullout of US forces which have served as a buffer.

"The Hajin battles continues," said Mustefa Bali, a spokesman for the Kurdish-dominated force, referring to the main front against IS in the Euphrates Valley.

"The US decision is just a decision and does not yet affect the situation on the ground," Bali told AFP.

According to the Syrian Observatory for Human Rights, fighting was ongoing on Thursday.

Backed by air strikes from the US-led coalition, SDF forces last week seized Hajin, the largest village in the last pocket of territory still controlled by IS in eastern Syria.

Hundreds of die-hard jihadists, however, have regrouped in Sousa and Al-Shaafa, the last two hubs in the ever-shrinking rump of the group's once sprawling "caliphate".

"We have previously said that, if attacked, we would dedicate ourselves to the defence of our land," Bali said.

"The scenario of a halt in the anti-terrorist battle is tied to Turkish threats," the SDF spokesman added.

He also hinted the US pullout, which many Kurds see as a betrayal, could make Syria's autonomous Kurdish administration less inclined to retain custody of detained IS fighters whom Western countries do not want to return home.

Bali did not suggest the Kurds would release detained jihadists but argued that Turkey risked targeting prisons in order to wreak chaos.

"Of course, if Turkey attacks, it will affect the fate of these prisoners," he said. "Turkey may target these prisons as it tries to release these terrorists."

The Kurds have repeatedly complained they do not have the capacity to handle the burden of more than 3,000 IS detainees and family members, urging Western powers to repatriate their nationals for trial at home.

Wester powers, including countries with significant contingents of captured foreign fighters such as France, have been reluctant to take back jihadists.