Iraqi forces engage in street warfare in west Mosul to cut casualties

Federal police members ride in the back of a vehicle during clashes between Iraqi forces and Islamic State militants, in Mosul, Iraq March 25, 2017. [Photo/Agencies]

"Nothing in this conflict is more important than protecting civilians. All parties of the conflict are obliged to do everything possible to protect civilians. This means that combatants cannot use people as human shields and cannot imperil lives through indiscriminate use of fire power," Grande said.

Meanwhile, Bruno Geddo, the representative of the UN Refugee Agency in Iraq, warned that an estimated 400,000 Iraqi civilians are trapped in Mosul's old city in northern Iraq as fighting intensifies and people continue to flee.

"The worst is yet to come," he said. Speaking by phone with the UN News Center, Geddo said the fighting in the west of the city has been more intense than the less densely populated east, where the battle ended in January.

"People are stuck between a rock and a hard place," he said. "There's fighting shelling, bombing."

"When people try to flee, extremists shoot them. Some have tried to leave during prayers or under cover of fog at first light, but were killed," Geddo added.

On Tuesday, Jasim al-Attiyah, deputy minister of the Iraqi Migration and Displaced Ministry, told Xinhua that the fierce battles brought the total number of civilians who left their homes in Mosul's both eastern and western sides to 415,000 since the beginning of the military offensive in October to reclaim the IS's largest stronghold in Iraq.

Iraqi Prime Minister Haider al-Abadi, who is also 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.

Late in January, Abadi declared the liberation of Mosul's eastern side, or the left bank of Tigris, after over 100 days of fighting IS militants.

However, Mosul's heavily-populated western part with its narrow streets appears to be a bigger challenge to Iraqi forces.

Mosul, 400 km north of the Iraqi capital of Baghdad, has been under IS control since June 2014, when government forces abandoned their posts and fled, enabling IS militants to take control of parts of Iraq's northern and western regions.