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.
Search operations by the security forces resulted in the arrest of 81 of the fugitives, it added.
The SDF said it had lost control of Shaddadi prison in the afternoon after “Damascus-affiliated factions” mounted a series of attacks and killed dozens of its fighters, who it said had been attempting to “prevent a serious security catastrophe”.
SDF spokesman Farhad Shami said around 1,500 IS members had 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 holding IS members and leaders.
IS has been weakened in Syria, but still remains active, predominantly carrying out attacks against Kurdish-led forces in the north-east in 2025.
The US was once the SDF’s main ally in Syria. In 2025, the US and partner forces said they had detained more than 300 IS operatives in Syria and killed over 20 during the same period.
However US special envoy Tom Barrack says the rationale for the US-SDF partnership has “largely expired”, and that his country was currently focused on ensuring the security of facilities holding IS prisoners and facilitating talks between the SDF and President Ahmed 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.