The SDF announced 40 of its members were killed during the People’s Hammer Operation, the name given to the ops to regain control of the prison located in the neighborhood of Ghweiran in the northeast Syrian city.

There were also 77 members of staff and guards at al-Sinaa prison who were killed during the clashes, as well as four civilians.

Tunnels were discovered inside some houses in Ghweiran in the vicinity of the prison and the adjacent neighborhood of al-Zuhour, which the SDF said were dug to back the sleeper cells’ attack on the prison.

"The attack was not a local attack, nor could it be limited to the prison alone,” the SDF said in the group’s statement.

The SDF announced on Sunday the conclusion of a "sweep campaign” in al-Sinaa, "after ending the last pockets in which Daesh terrorists were present in the northern dormitories.”

Kurdish forces reported days earlier that a group of 60-90 armed men were barricaded in one of the northern dormitories.

The Coordination and Military Ops Center of SDF said on Monday 27 ISIS "operatives and suspects” were arrested during operations in the countryside of Raqqa. The SDF and Internal Security Forces (ISF) were searching for ISIS cells in villages and camps, Hawar News Agency said.

North Press Agency said hundreds of ISIS members were arrested during combing operations in Hasaka neighborhoods, noting two ISIS members in the neighborhood of Aziziyah were caught wearing explosive belts.

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