Around 400,000 people are "trapped" in the Islamic State-controlled Old City of west Mosul, the UN said.

The UN refugee agency (UNHCR) warned that food and medical shortages and sustained shelling could provoke a mass exodus.

An agency official in Iraq, Bruno Geddo, said: "The worst is yet to come."

Last month the Iraqi government launched an offensive to recapture west Mosul, which is the last major urban centre controlled by IS.

Image: An Iraqi Air Force helicopter fires missiles against Islamic State militants in Mosul Image: A sniper takes aim during the advance into the Old City in west Mosul Image: Smoke rises from clashes near Mosul's Al-Habda minaret at the Grand Mosque Image: A displaced Iraqi man, who fled his home, carries his child near Badush Image: Cars burnt and destroyed by clashes on a street Image: A tank of Iraqi rapid response forces fires against IS militants in the Bab al-Tob area Image: Federal police members fire their weapons during a battle against IS militants Image: Displaced Iraqis wait to enter the Hammam al-Alil camp Image: Destruction in the al-Dawasah neighbourhood. Continue through for more pictures... Image: A member of the Iraqi forces raises a battered national flag on the outskirts of the old city /

Fighting has intensified in recent days as the government forces have retaken a series of neighbourhoods from IS, but the militants still hold an estimated 40% of western Mosul.


:: Mosul: No safe areas for civilians in a city 'being reduced to rubble'

The UN says 600,000 people are still in IS-controlled areas, including 400,000 trapped in siege-like conditions.

"They are desperate for food. They are panicked," said Mr Geddo, speaking from the Hammam al-Alil camp for people displaced by the fighting, a few miles south of Mosul.

"There is a shortage of fuel, of food, of electricity.

"People have resorted to burning furniture, old clothes, anything they can use to keep warm at night, because it is still raining heavily and the temperatures at night in particular drop significantly," he said.

He said many people were surviving on just bread and water, and eating once a day.

Sky News team has narrow escape in Mosul

Medical charity Doctors Without Borders have reported treating children for "severe malnutrition" after they escaped the city.

The UN says many people are scared to leave their homes because of Islamic State snipers, but around 157,000 have reached a transit centre since the offensive began.

Between 8,000 and 12,000 people were now arriving at the transit centre each day, Mr Geddo said.

He said those who were making it through were telling staff at the centre they preferred "to take the risk of dying while I stand a chance to be free and safe again with my family".