A United Nations' aid agency on Monday said that nearly half a million people have been displaced in six months of an offensive to dislodge the Islamic State (IS) militants from their last major stronghold in Iraq's northern city of Mosul.
Hundreds of thousands more may flee their homes in the coming weeks, the United Nation's Office for the Coordination of Humanitarian Affairs (OCHA) said in a statement.
"Our worst case scenario when the fighting started was that up to one million civilians may flee Mosul. Already, more than 493,000 people have left, leaving almost everything behind," the statement quoted Lise Grande, the Humanitarian Coordinator for Iraq, as saying.
"The sheer volume of civilians still fleeing Mosul city is staggering," Grande said.
According to the statement, there are still some 500,000 people trapped in their homes in the IS-controlled neighborhoods in the western side of Mosul, including 400,000 in the densely populated old city center.
The international humanitarian aid agencies are working around-the-clock to expand the emergency sites and camps to shelter the hundreds of thousands more who may flee their homes in coming days and weeks, the statement said.
"Mosul has pushed us to our operational limits as 1.9 million people have received life-saving assistance since the fighting began," Grande said.
"We're doing everything we can but this has been a long battle and the assault on the old city hasn't started," Grande warned, pointing out that the battles in the western side of Mosul is very different than in the east.
"It's much tougher. There are more trauma injuries, homes are being destroyed, food stocks are dwindling quickly and families are at serious risk because there isn't enough drinking water," she said.
"Civilians in Mosul face incredible, terrifying risks. They are being shot at, there are artillery barrages, families are running out of supplies, medicines are scarce and water is cut-off," Grande added.
The international humanitarian law obliges all parties in the conflicts to protect civilians, and to ensure that innocent people can get the assistance they need and limit damage to civilian infrastructure.
"Nothing is more important than protecting civilians. Nothing," Grande concluded.
OCHA statement came as fierce battles are underway to drive out the extremist IS militants from the western side of Mosul, including the densely-populated old city center with its old houses at the maze-like narrow allies.
The progress in the old city center is much slower than the early phases of the offensive as the IS militants showed stubborn resistance, while the troops were forced to restrict the use of bombs and increased sniper fire against terrorist militants holed up in the city center.
Iraqi Prime Minister Haider al-Abadi, who is also the commander-in-chief of the armed forces, announced the start of an offensive on February 19 to drive extremist militants out of the western side of Mosul, locally known as the right bank of Tigris River which bisects the city.
Late in January, Abadi declared the liberation of the eastern side of Mosul, or the left bank of Tigris, after more than 100 days of fighting against IS militants.
Mosul, 400 km north of the Iraqi capital of Baghdad, has been under IS control since June 2014, when government forces abandoned their weapons and fled, enabling IS militants to take control of parts of Iraq's northern and western regions.

source: Xinhua