"They are in control of a portion of the city," US Defence Secretary Ashton Carter told reporters at the Pentagon. "It's too early to say all of the city." Iraqi security forces celebrate in central Fallujah, Iraq, after fighting against the Islamic State militants. Credit:AP Fallujah's fall to the Islamic State in late 2013 marked the start of the group's rise in Iraq. Its ability to keep hold of the city, around 65 kilometres to the west of the capital, Baghdad, has been seen as a major test of the Islamic State's staying power. At the same time, the city's recapture is critical for a government trying to reassert territorial sovereignty and launch an offensive on the jihadist group in Mosul, to the north. "While the capture of Fallujah would inflict a heavy blow on Islamic State, it is quite early to declare a victory there," said Nihat Ali Ozcan, a strategist at the Economic Policy Research Foundation in Ankara, Turkey. "The battle to retake larger Mosul will be even more difficult, and could prove to be a real challenge." The offensive against Fallujah began on May 22, and while much of the fighting in surrounding villages was carried out by Shiite militias with Iranian military advisers, the assault on the city itself fell to Iraqi government forces backed by air support from the U.S. and allies.

As the Islamic State's resistance in Fallujah crumbled, its fighters fled, disguised as women, the Iraqi army said on Friday. Iraqi special forces entered the center of Fallujah city early on Friday, taking over a government complex and a neighborhood that served as a base for Islamic State. Credit:AP The United Nations and humanitarian groups have expressed concern about the fate of civilians trapped inside the city, who have dwindling access to food and clean water. About 43,000 civilians have fled the fighting in Fallujah, while about 50,000 remain trapped, the UN said on June 13. Earlier this week, the Iraqi army said it had secured the first safe route for residents out of the city. Islamic State fighters had prevented residents from leaving, using them as human shields and playing on fears that Shiite militias would carry out revenge attacks on the predominantly Sunni residents. Iraqi security forces enter central Fallujah after fight against the Islamic State militants on Friday. Credit:AP

Even as the battle appeared far from over, Iraqi commanders on the ground were optimistic that the advance, which had slowed in the face of Islamic State snipers, roadside bombs and tunnel networks that allowed fighters to move around undetected, would continue. "ISIS has lost its power to defend Fallujah," Colonel Jamal Lateef, a police commander in Anbar Province, said in an interview. "Its defensive lines have collapsed, and the battle of Fallujah will be over in no time." An Iraqi forces tank moves into Fallujah, Iraq. Credit:AP Lieutenant General Adbulwahab al-Saadi, a commander of Iraq's counter-terrorism forces who is in charge of the Fallujah operation, said in a brief telephone interview that, "ISIS has collapsed in Fallujah very fast," and he said his forces were moving to northern and western neighbourhoods. The United States, which has led a coalition targeting the Islamic State with airstrikes for almost two years in Iraq, has supported the battle for Fallujah with air power, In a statement released on Friday, the US military said it had struck two targets near Fallujah on Thursday, destroying six heavy machine guns and 10 Islamic State fighting positions.

Iraqi security forces fire at Islamic State militants in Fallujah. Credit:AP Fallujah was a stronghold, and something of a birthplace, for al-Qaeda in Iraq, the precursor of Islamic State, that formed to fight the United States after the invasion of 2003. Officials speculated that the change in the complexion of the battle might have been because local tribal fighters who had been loyal to the Islamic State's leadership and its transnational ambitions had now distanced themselves from the group's foreign fighters. Or at least, the officials surmised, the tribal fighters had come to believe that victory by the Iraqi government was inevitable and were trying to get their families to safety. Smoke rises after an airstrike as Iraqi security forces advance. Credit:AP Lise Grande, the United Nations' humanitarian co-ordinator for Iraq, said she was receiving reports that perhaps 10,000 families, or 60,000 people, were on the move toward government-held areas of western Anbar Province, where camps for the displaced are already overwhelmed and lack basic supplies, such as tents and clean drinking water.

Karl Schembri, a spokesman for the Norwegian Refugee Council in Baghdad, said that, beginning on Thursday, Islamic State militants had been withdrawing from positions inside the city, allowing civilians to begin fleeing. Fallujah has been locked in a cycle of conflict since 2003. Credit:AP Mr Schembri said they had withdrawn from checkpoints at two bridges on the Euphrates, "and then people could just walk out." He expressed concern for the thousands of civilians stuck in the city, including those that are unable to walk out on their own — the elderly, disabled and pregnant. Referring to the militants, he said, "we don't know where they have gone to or what their plan is." Sajad Jiyad, who runs an Iraqi research organisation, the Al-Bayan Centre and who sometimes advises the office of Mr Abadi, wrote on Twitter on Friday, referring to the Arabic acronym for the Islamic State, "Daesh fighters escaping as civilians is a massive concern."

Bloomberg, The New York Times