'Race against clock' to prepare for exodus from west Mosul advance

The United Nations is rushing to build more shelters around Mosul ahead of an expected wave of displacement from the city, the Islamic State (IS) group's last stronghold in Iraq.

The scramble comes as Iraqi forces begin their advance on the western half of Mosul, home to the narrow streets of the Old City, thought to be the toughest nut to crack in the Iraqi government's months-long attempt to retake the city.

"We are racing against the clock to prepare emergency sites south of Mosul to receive displaced families," said the UN's humanitarian coordinator in Iraq, Lise Grande, in a statement.

"The humanitarian operation is already stretched. We are trying to reach more than six million people across Iraq who need help. We don't have all of the funding we need and many partners are facing major capacity constraints," she said.

Aid organisations had feared an exodus of unprecedented proportions before the start of the Mosul operation, but so far half a million - a significant majority - of residents have stayed home.

Their continued presence prevented both sides from resorting to deadlier weaponry, which may have slowed the battle but averted a potentially much more serious humanitarian emergency in the middle of winter, as well as more extensive material damage to the city.

Residents of west Mosul have reported very difficult living conditions and have warned that they were already low on food, with weeks of fighting expected to lie ahead.

Grande told AFP that, while the Mosul operation is going "better than expected," there are still "serious dangers" lying ahead. 

West Mosul offensive begins

Iraqi forces launched their offensive on IS militants defending Mosul's west bank on Sunday.

"Our forces are beginning the liberation of the citizens from the terror of Daesh," Iraqi Prime Minister Haider al-Abadi said in a short televised speech, using an Arabic acronym for IS.

"We announce the start of a new phase in the operation. We are coming, Nineveh, to liberate the western side of Mosul," he said, referring to the province of which Mosul is the capital.

Federal police and interior ministry forces were expected to start the new phase in the offensive by moving on Mosul airport, which is on the southern edge of the city, west of the Tigris River.

'House-to-house fighting on a bloody scale'

The militants have put up stiff resistance defending Mosul, their last major stronghold in Iraq and the place where their leader Abu Bakr al-Baghdadi proclaimed a "caliphate" in 2014.

After shaping operations around Mosul, it took Iraq's most seasoned forces - the elite Counter-Terrorism Service (CTS) - more than two months to clear the eastern side of the city.

After a pause in the operation launched on 17 October, federal forces now face what was always billed as the toughest nut to crack: Mosul's west bank, home to the narrow streets of the Old City.

"West Mosul had the potential certainly of being more difficult, with house-to-house fighting on a larger and more bloody scale," said Patrick Skinner, from the Soufan Group intelligence consultancy.

The streets around the historical centre, which includes the mosque in which Baghdadi made his only public appearance in June 2014, will be impassable for many military vehicles and force government fighters to take on IS in perilous dismounted warfare.

Prior to the offensive that saw IS seize Mosul and much of Iraq's Sunni Arab heartland almost three years ago, the east bank was more ethnically diverse than the west, where analysts believe the militants may enjoy more support.

"IS resistance could be greater in this area and it will be harder, but all the more important, to completely clear the networks from Mosul after its recapture," said Emily Anagnostos, Iraq analyst at the Institute for the Study of War.

While the federal forces' attrition is said to be high, IS's has been undoubtedly higher, and commanders have said the militants may no longer have the resources to defend east Mosul effectively. 

IS fighters and Mosul residents remained able to move across both sides of the city during much of the fighting, but all bridges across the Tigris have now been dropped and the militants in the west are all but besieged.

IS has used civilians as human shields as part of its defence tactics and killed residents attempting to flee, making it both difficult and dangerous for the population to escape.

While specialised units may attempt to throw pontoon bridges across the river to attack from the east, the main initial assault of the upcoming phase in Mosul is expected to come from the south on the city's airport.

Army, police, interior ministry and special forces have been gearing up for the push on Mosul's southern front, with a large concentration of fighters based out of Hammam al-Alil.