MOSUL/ERBIL, Iraq (Reuters) - The United Nations said on Tuesday it was expanding camps for people fleeing Mosul, as air strikes resumed on Islamic State positions in Iraq’s second largest city.

An Iraqi boy sits on a piece of debris in a street of Mosul, Iraq, April 4, 2017. REUTERS/Andres Martinez Casares

More than 300,000 people have fled Mosul since the start of the U.S.-backed campaign in October, the office of the U.N. Humanitarian Coordinator in Iraq said in a statement.

Before the operation to drive Islamic State from the city began, Mosul had a population of about a million and half, split about evenly between the areas east and west of the Tigris river that runs through the middle.

Iraqi forces captured the eastern side in January and in February launched a second phase to take the western side, with air and ground support from a U.S.-led coalition.

They are now battling to take the northwestern part, but the civilian death toll has mounted in the old city, where the militants are dug in amongst residents.

More people are expected to flee the fighting and camps for the displaced north and east of Mosul are expanding, the U.N. statement said.

Air strikes on the city by the Iraqi air force resumed on Tuesday as the sky cleared after several days of bad weather, the Iraqi military said.

The Iraqi air force carried out at least three air strikes in western Mosul, killing several dozens of Islamic State fighters, according to Iraqi military statements on Tuesday.

A number of Islamic State commanders were killed in an air strike on a position in Hay al-Tanak, a stronghold of the group, they said.

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Among those killed were commanders in charge of booby traps, of Arab suicide fighters and child recruitment, the statement added, without identifying them by name. The two other strikes killed militants and destroyed weapons and vehicles.

Islamic State’s media outlets did not mention the strikes when they aired comments from Abi al-Hassan Al-Muhajer, who took over the role of spokesman after the death last year of the group’s notorious media head, Abu Mohammad al-Adnani, in an air strike.

“O soldiers of the caliphate, beware not to withdraw from any inch before turning it into hell,” he said in an audio recording on Telegram, echoing a similar call made by Islamic State leader Abu Bakr al-Baghdadi when the campaign on Mosul started.

“Ambush them in the houses, the alleyways and the streets, mine the arcades and carry out raid after raid,” he said.

“NO FOOD”

A Reuters TV crew saw dozens of people fleeing their homes near or across the frontline, braving sniper and mortar fire, while a helicopter strafed positions further north.

“Shells were falling on us and there is no food, no water, no electricity,” said Hamda Bakheet, a woman in her mid-60s from the Nablus district, adding that the militants were firing on people who leave the city.

Bakheet said one of her sons was killed when the Islamists first overran Mosul and the other was accused of being a “renegade” and jailed a year ago. “I hope the army will free him soon.”

The improved weather should also allow ground forces to resume their advance toward the Grand al-Nuri Mosque, where Baghdadi, declared a “caliphate” nearly three years ago over parts of Iraq and Syria.

Heavy fighting with machine guns, rocket propelled grenade launchers and mortars was heard by the Reuters TV crew coming from the area around the mosque, located in the old city and famous for its leaning minaret.

The current phase of the campaign is the most difficult as narrow alleyways in the densely populated old city limit the use of artillery, air power and armoured vehicles.

An explosion in western Mosul last month killed between 60 and 240 people, according to various accounts.

U.S. President Donald Trump’s son-in-law, Jared Kushner, flew into Iraq on Monday with the top U.S. general to get a first-hand assessment of the battle against Islamic State from U.S. commanders on the ground and Iraqi leaders.

The trip comes as Trump examines ways to accelerate a campaign that U.S. and Iraqi officials say has so far largely succeeded in uprooting Islamic State in Iraq and Syria.

In the first official remarks by the group referring to Trump since he took office, the Islamic State spokesman Al-Muhajer said: “... You (the U.S.) are bankrupt and the signs of your demise are evident to every eye.”

“... There is no more evidence than the fact that you are being run by an idiot who does not know what Syria or Iraq or Islam is,” he said.