Updated: June 8, 2016 at 4:03 PM

Iraqi security forces clash with Islamic State militants in Fallujah (15 images)

Iraqi security forces, aided by Shiite militias, continued in their efforts to retake the city of Fallujah from the Islamic State.

Gains made by security forces have been marred by accusations that Shiite militias have tortured captured civilians fleeing the besieged city in western Anbar Province.

Iraqi security forces and members of the Popular Mobilization Forces (a government-sponsored Shiite militia), are pictured in front of the tattered remains of an Islamic State flag hanging from the side of a building in the Shuhadaa neighborhood of Fallujah following clashes with Islamic State militants on June 7, 2016. Photo by Abbas Mohammed /UPI

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Iraqi security forces, with heavy weaponry in tow, are pictured on the outskirts of town prior to clashes with Islamic State militants in the Shuhadaa neighborhood of Fallujah on June 7, 2016. The operation to retake Fallujah, a key city in the western part of Anbar Province, is expected to be one of the most difficult faced by the central government. Photo by Abbas Mohammed /UPI

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Members of the Iraqi security forces are seen running through the Shuhadaa neighborhood of Fallujah during clashes with Islamic State militants on June 7, 2016. The operation to retake Fallujah, a key city in the western part of Anbar Province, is expected to be one of the most difficult faced by the central government. Photo by Abbas Mohammed /UPI

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Members of the Iraqi security forces are seen moving towards the front lines in the Shuhadaa neighborhood of Fallujah during clashes with Islamic State militants on June 7, 2016. The operation to retake Fallujah, a key city in the western part of Anbar Province, is expected to be one of the most difficult faced by the central government. Photo by Abbas Mohammed /UPI

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Iraqi security forces clash with Islamic State militants in Fallujah (15 images)

Iraqi security forces, aided by Shiite militias, continued in their efforts to retake the city of Fallujah from the Islamic State. Gains made by security forces have been marred by accusations that Shiite militias have tortured captured civilians fleeing the besieged city in western Anbar Province.