Iraq’s Supreme Judicial Council announced Sunday that it will prosecute and try Islamic State militants being transferred from prisons and detention camps in Syria under a U.S.-brokered deal. The decision came as the U.S. military moved hundreds of the approximately 9,000 Islamic State detainees held in Syria since the militant group’s collapse there in 2019.

The transfers respond to recent developments in Syria, where the country’s new military forces last month seized control of major detention facilities from Kurdish-led fighters who had guarded the camps for years.

Syria’s military took control of the sprawling al-Hol camp — housing thousands of people, mostly families of IS militants — and a prison in the northeastern town of Shaddadeh from the Syrian Democratic Forces (SDF) following clashes that pushed the Kurdish-led fighters from areas they had controlled since the U.S.-backed fight against IS. The SDF withdrew as part of a ceasefire. Some IS detainees escaped during the fighting, though Syrian state media reported that many were recaptured.

The takeover prompted fears that IS might activate its sleeper cells in those areas or that detainees could escape and regroup. Iraq, which shares a long border with Syria, has been particularly concerned that escaped IS militants could reorganize and threaten its security.

Syria’s Takeover Spurs Prisoner Transfer

The U.S. military started transferring detainees Friday. By Sunday, 275 IS prisoners had been moved to Iraq, with 125 transferred that day, according to two Iraqi security officials. The officials said the process has been slow, as the U.S. military is transporting detainees by air.

Transfers Begin on Large Scale

Once in Iraq, detainees accused of terrorism will be investigated by Iraqi security forces and tried in Iraqi courts under the country’s domestic legal system, according to the Supreme Judicial Council. Both the Syrian government and Washington have welcomed Baghdad’s offer to receive the prisoners.

IS Threat Persists Despite Territorial Defeat

The Islamic State was defeated in Iraq in 2017 and in Syria two years later, though IS sleeper cells continue to carry out attacks in both countries. During the fight against IS, thousands of extremists and tens of thousands of women and children associated with the group were captured and held in the Syrian prisons and camps. Last year, U.S. troops and their SDF partners detained more than 300 IS militants in Syria and killed more than 20. An IS ambush in December killed two U.S. soldiers and one American civilian interpreter in Syria.

Iraq’s parliament was scheduled to meet later Sunday to discuss the ongoing developments in Syria, where the government is working to increase its military presence along the border. The ceasefire between Syrian forces and the SDF has been extended to support the U.S.-led prisoner transfer operation.