The decision to move prisoners of the Islamic State group from northeast Syria to detention centers in Iraq came after a request by officials in Baghdad that was welcomed by the U.S.-led coalition and the Syrian government, officials said Thursday.

American and Iraqi officials told The Associated Press about the Iraqi request, a day after the U.S. military said that it started transferring some of the 9,000 IS detainees held in more than a dozen detention centers in northeast Syria controlled by the Kurdish-led Syrian Democratic Forces, or SDF.

The move to start transferring the detainees came after Syrian government forces took control of the sprawling al-Hol camp — which houses thousands of mostly women and children — from the SDF, which withdrew as part of a ceasefire. Troops on Monday seized a prison in the northeastern town of Shaddadeh, where some IS detainees escaped and many were recaptured, state media reported.

The SDF said Thursday that government forces shelled al-Aqtan prison near the northern city of Raqqa with heavy weapons, while simultaneously imposing a siege around the prison using tanks and deploying fighters.

Al-Aqtan prison, where some IS prisoners are held, was surrounded by government forces earlier this week and negotiations were ongoing on the future of the detention facility.

With the push by government forces into northeast Syria along the border with Iraq, there have been concerns in Baghdad that some of the detainees might become a danger to Iraq’s security, if they manage to flee from the detention centers amid the chaos.

An Iraqi security official said that the decision to transfer the prisoners from Syria to Iraq was an Iraqi decision, welcomed by the U.S.-led coalition and the Syrian government. The official added that it was in Iraq’s security interest to detain them in Iraqi prisons rather than leaving them in Syria.

Also Thursday, a senior U.S. military official confirmed to the AP that Iraq “offered proactively” to take the IS prisoners rather than the U.S. requesting it of them.

Both the Iraqi and U.S. officials spoke on condition of anonymity because they weren't authorized to comment publicly.

Over the past several years, the SDF has handed over to Iraqi authorities foreign fighters, including French citizens, who were put on trial and received sentences.

The SDF still controls more than a dozen detention facilities holding around 9,000 IS members, but is slated to hand the prisons over to government control under a peace process that also is supposed to eventually merge the SDF with government forces.

U.S. Central Command said that the first transfer on Wednesday involved 150 IS members, who were taken from Syria’s northeastern province of Hassakeh to “secure locations” in Iraq. The statement said that up to 7,000 detainees could be transferred to Iraqi-controlled facilities.

IS declared a caliphate in 2014 in large parts of Syria and Iraq, attracting large numbers of fighters from around the world. The group was defeated in Iraq in 2017, and in Syria two years later, but its sleeper cells still carry out deadly attacks in both countries. The SDF played a major role in defeating IS.

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Abby Sewell reported from Beirut.