The US military has begun the transfer up to 7,000 Islamic State (IS) group detainees from prisons in north-eastern Syria to Iraq, as Syria’s new government takes control of areas long run autonomously by Kurdish-led forces.

US Central Command (Centcom) said it had already moved 150 IS fighters from Hassakeh province to a “secure location” in Iraq.

It said the move aimed to prevent prisoners breaking out and regrouping.

The transfer follows a ceasefire agreement that has brought much of Syria’s north east under Damascus control, after the Kurdish-led Syrian Democratic Forces (SDF) withdrew from key areas, including detention sites holding thousands of IS suspects and their relatives.

CENTCOM said its commander Admiral Brad Cooper discussed the transfers with Syria’s new president Ahmed al-Sharaa, stressing the need for Syrian forces to uphold the ceasefire and avoid any action that could interfere with what he described as an “orderly and secure transfer” of detainees.

Rights group Reprieve warned that detainees transferred to Iraq could face torture and execution and urged the UK government to establish whether any British nationals were among those being moved.

The charity said it believed there were no more than 10 British men held in the prisons, though exact numbers were unclear. Around 55 to 60 British nationals, most of them children, remain detained across camps and prisons in the region, it said.

Despite the ceasefire there have been fresh clashes, with Syria’s defence ministry saying seven soldiers were killed in a drone attack in Hassakeh on Wednesday, describing the incident a violation of the ceasefire.

The SDF denied carrying out the strike and accused Damascus of also launching attacks, including near the town of Kobane on the Turkish border.

The government and SDF had earlier blamed each other over the escape of suspected IS fighters from an SDF-run prison in Shaddadi, in southern Hassakeh.

Syria’s interior ministry said on Monday night that its special forces and army soldiers had entered the town following “the escape of around 120 [IS] terrorists” from the prison. It said security forces later recaptured 81 of the fugitives.

The SDF said it had lost control of the prison following clashes with “Damascus-affiliated factions”, warning of a “serious security catastrophe”.

SDF spokesman Farhad Shami said around 1,500 IS members may have escaped during the clashes, according to Reuters news agency. The SDF also accused government forces of attacking al-Aqtan prison, north of the city of Raqqa, which is also holding IS members and leaders.

The SDF helped US-led forces defeat IS during Syria’s 13-year civil war and, backed by the US, went on to jail around 12,000 IS members, including thousands of foreigners, while detaining tens of thousands of relatives in camps across the north east.

However US special envoy Tom Barrack has said the US alliance with the SDF had “largely expired” and that his country was currently focused on securing IS detention facilities and facilitating talks between the SDF and al-Sharaa’s government.

“This moment offers a pathway to full integration into a unified Syrian state with citizenship rights, cultural protections, and political participation – long denied under Bashar al-Assad’s regime,” he wrote on X.