Terrified residents are streaming out western Mosul's al-Zanjili district with whatever possessions they can carry as Iraqi forces bombard Isis positions with mortars as part of an operation to capture the militants' last held enclave in the city.

Mosul residents flee Islamic State Isis Daesh
A member of the Iraqi forces loads a mortar as residents evacuate from western Mosul's al-Zanjili neighbourhoodKarim Sahib/AFP
Mosul residents flee Islamic State Isis Daesh
Members of the Iraqi forces fire mortar shells during battles in western Mosul's al-Zanjili neighbourhoodKarim Sahib/AFP
Mosul residents flee Islamic State Isis Daesh
A man carrying his baby flees his home during a fight between Iraqi forces and Islamic State militantsAlaa al-Marjani/Reuters
Mosul residents flee Islamic State Isis Daesh
An Iraqi woman who fled her home in al-Zanjili neighbourhood carries a mattressAlaa al-Marjani/Reuters
Mosul residents flee Islamic State Isis Daesh
A displaced Iraqi boy carries a clock as he flees from western MosulAlkis Konstantinidis/Reuters
Mosul residents flee Islamic State Isis Daesh
An Iraqi family flees in a vehicle that was damaged in battle while evacuating from western Mosul's al-Zanjili neighbourhoodKarim Sahib/AFP
Mosul residents flee Islamic State Isis Daesh
A displaced Iraqi boy carries a chicken while evacuating his home in western Mosul's al-Zanjili neighbourhoodKarim Sahib/AFP
Mosul residents flee Islamic State Isis Daesh
A child wearing one shoe flees Mosul's al-Zanjili neighbourhoodAlaa al-Marjani/Reuters

Progress has been slowed down by the presence of civilians, an Iraqi government adviser told Reuters. Iraqi forces have been dropping leaflets in districts telling families to flee, but although about 700,000 people have already fled, many have remained over fear of getting caught in the crossfire.

Up to 200,000 people still live in harrowing conditions behind Isis lines in Mosul, running low on food, water and medicine, and with difficult access to hospitals, the United Nations said.

Mosul residents flee Islamic State Isis Daesh
Residents of Mosul's al-Zanjili neighbourhood flee during a fight between Iraqi forces and Isis militantsAlaa al-Marjani/Reuters
Mosul residents flee Islamic State Isis Daesh
A woman in a wheelchair carrying a baby is helped to flee the fighting in the Old City of MosulAlaa al-Marjani/Reuters
Mosul residents flee Islamic State Isis Daesh
Displaced Iraqi people who fled their homes during a fight between Iraqi forces and Islamic State militants arrive in al-Zanjili neighbourhood, north of Mosul's Old CityAlaa al-Marjani/Reuters
Mosul residents flee Islamic State Isis Daesh
Iraqi people who fled their homes ride in a car during a fight between Iraqi forces and Isis militantsAlaa al-Marjani/Reuters
Mosul residents flee Islamic State Isis Daesh
Displaced Iraqi people carry their belongings as they flee the fighting in western MosulAlkis Konstantinidis/Reuters
Mosul residents flee Islamic State Isis Daesh
A displaced Iraqi boy carries his belongings while evacuating from western Mosul's al-Zanjili neighbourhoodKarim Sahib/AFP
Mosul residents flee Islamic State Isis Daesh
A displaced Iraqi woman carrying her belongings walks past the twisted wreckage of a carKarim Sahib/AFP
Mosul residents flee Islamic State Isis Daesh
An Iraqi boy carries a ceiling fan while fleeing the fighting in western Mosul's al-Zanjili neighbourhoodKarim Sahib/AFP
Mosul residents flee Islamic State Isis Daesh
Iraqi people are given bottles of water after they fled their homesAlaa al-Marjani/Reuters
Mosul residents flee Islamic State Isis Daesh
A woman is given water after collapsing in Mosul's al-Zanjili neighbourhoodAlaa al-Marjani/Reuters
Mosul residents flee Islamic State Isis Daesh
An Iraqi man who fled his home reacts during a fight between Iraqi forces and Islamic State militantsAlaa al-Marjani/Reuters

The Mosul offensive, now in its eighth month, has taken much more time than expected because Isis is fighting in the middle of civilians and using them as human shields. Over the past few days, the militants ordered dozens of families living in al-Zanjili district to move into the Old City to prevent them from escaping toward the Iraqi forces trying to advance from the northern side, a resident said.

Isis fighters have closed the streets around the Great Mosque of al-Nuri, residents said, apparently in preparation for a final showdown in the battle over their last major stronghold in Iraq. Dozens of fighters were seen by residents taking up positions around the medieval mosque, the site where Isis leader Abu Bakr al-Baghdadi declared an Islamist caliphate in July 2014. Islamic State's black flag has been flying from the mosque since the militants captured Mosul and seized swathes of Iraq and Syria three years ago.

Mosul residents flee Islamic State Isis Daesh
A black jihadist flag hangs from Mosul's Al-Habda minaret at the Great Mosque of al-Nuri, where Isis leader Abu Bakr al-Baghdadi declared his caliphate back in 2014Alkis Konstantinidis/Reuters

The Grand al-Nuri Mosque has become a symbolic focus of the campaign, with Iraqi commanders privately saying they hope to capture it during Ramadan. However, a battle in or near the mosque would put the building and its famed leaning minaret at risk, experts have said. The minaret, several feet off the perpendicular and standing on humid soil, is particularly vulnerable as it has not been renovated since 1970. Its tilt gave the landmark its popular name - al-Hadba, or the hunchback.

"Daesh's fighters know that the mosque is the most important target and they are preparing for a major battle there," said Hisham al-Hashemi, who advises several Middle East government including Iraq's on Isis affairs.

Mosul residents flee Islamic State Isis Daesh
A member of the Iraqi forces fires a mortar shell during a battle in western Mosul's al-Zanjili neighbourhoodKarim Sahib/AFP
Mosul residents flee Islamic State Isis Daesh
A view along a debris-strewn street in west MosulAlkis Konstantinidis/Reuters
Mosul residents flee Islamic State Isis Daesh
Smoke billows near western Mosul's al-Shifa hospital during ongoing battles between Iraqi forces and Islamic State fightersKarim Sahib/AFP

The fall of Mosul would, in effect, mark the end of the Iraqi half of the self-styled caliphate. Meanwhile in Syria, Kurdish forces backed by US air strikes are besieging Isis in the city of Raqqa, the militants' de facto capital in that country.