Iraqi forces have been closing in on Fallujah in order to reclaim the city from Islamic State (Isis) militants in what has been described as one of the biggest battles ever fought between IS militants. Fallujah was the first city in Iraq to fall under IS control in January 2014 and has been under siege for more than six months.

On Tuesday (31 May 2016), Iraqi Shi'ite fighters repelled a four-hour attack in the city's south, a day after moving into the southern edges of the militant city, with the help of US-led coalition air strikes. Two officers with the Iraqi special forces told the Associated Press that the attack began in Fallujah's Nuaimiya area at dawn, where Iraqi troops captured almost 85% of the ground the day before.

The officers, speaking on the condition of anonymity, continued their account, saying that the militants used tunnels, deployed snipers and sent six cars filled with explosives towards Iraqi troops, which were destroyed before reaching the targets.

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An Iraqi Shi'ite fighter fires artillery during clashes with Islamic State militants near FallujahAlaa Al-Marjani/Reuters
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Shi'ite fighters and Iraqi security forces fire artillery during clashes with Islamic State militants near FallujahAlaa Al-Marjani/Reuters
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Military vehicles for Iraqi security forces and Shi'ite fighters are seen near FallujahAlaa Al-Marjani/Reuters
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Iraqi security forces sit in a military vehicle near FallujaAlaa Al-Marjani/Reuters

According to the UN refugee agency, the IS militants occupying Fallujah are holding several hundred families, using them as 'human shields' and depriving them of food, water and medicine. Some 3,700 people have managed to flee the besieged city during the week-long offensive, which began on 23 May. Yet it has been reported that some 50,000 people remain trapped in the city in what has been described as a "human catastrophe".

"UNHCR has received reports of casualties among civilians in the city centre of Fallujah due to heavy shelling, including seven members of one family on the 28th of May [Saturday]," UNHCR spokesman William Spindler said at a news briefing.

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Smoke rises from clashes near FallujahAlaa Al-Marjani/Reuters
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Shi'ite fighters fire artillery during clashes with Islamic State militants near FallujahAlaa Al-Marjani/Reuters
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Smoke rises from clashes near FallujahThaier Al-Sudani/Reuters
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Fighters from the Iraqi Shi'ite Badr Organisation walk past a poster depicting images of former Iraqi president Saddam Hussein on the outskirts of FallujahThaier Al-Sudani/Reuters

"Most people able to get out come from the outskirts of Fallujah. For some time militants have been controlling movements, we know civilians have been prevented from fleeing. There are also reports from people who left in recent days that they are being required to move with Isil [Isis] within Fallujah," UNHCR field staff, spokeswoman Ariane Rummery told Reuters.

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An Iraqi security forces member gestures near FallujahAlaa Al-Marjani/Reuters
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An Iraqi Shi'ite fighter covers his ear as artillery fires towards Islamic State militants near FallujahThaier Al-Sudani/Reuters
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A member of the Iraqi security forces ride atop a military vehicle near FallujahAlaa Al-Marjani/Reuters

If recaptured, Fallujah would be the third major city in Iraq to be regained by the government after Tikrit and Ramadi, the capital of Iraq's vast western Anbar province. Reclaiming it would give Masum's government control of the major population centres of the Euphrates River valley west of the capital for the first time in more than two years.

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A fighter from the Iraqi Shi'ite Badr Organization holds his rifle as he look a tunnel built by Islamic State fighters on the outskirts of FallujahThaier Al-Sudani/Reuters
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Military vehicles of the Iraqi security forces are seen near FallujahAlaa Al-Marjani/Reuters
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Iraqi security forces gather near FallujahAlaa Al-Marjani/Reuters
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Iraqi security forces and Shi'ite fighters sit in military vehicles near FallujahAlaa Al-Marjani/Reuters
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An Iraqi Shi'ite fighter fires artillery during clashes with Islamic State militants near FallujahAlaa Al-Marjani/Reuters
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Shi'ite fighters take photos of themselves while firing artillery towards Islamic State militants near FallujahAlaa Al-Marjani/Reuters
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Iraqi security forces gather near FallujahThaier Al-Sudani/Reuters
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Iraqi security forces serve food near FallujahAlaa Al-Marjani/Reuters