Up to 30 civilians have allegedly been killed in an air strike targeting an Isis commander in Mosul as Iraqi forces continue their advance into their city.

The US-led coalition is investigating whether its planes were responsible for the reported massacre in the al-Jadida district, which came as the UN warned that almost 50 per cent of all casualties in the military operation are believed to be civilians.

Witnesses said they saw at least three missiles hit the house of a senior Isis militant called Harbi Abdel Qader on Thursday.

Islamic State video purports to show fighting in Mosul

He was not inside the building at the time but several members of his family were among around 30 people who died, one resident told Reuters.

The Iraq Body Count group said at least 25 people were killed in the incident.

A spokesperson for US Central Command, which coordinates coalition air strikes, told The Independent it had bombed targets in the area on the day as part of numerous strikes targeting Isis fighters and infrastructure.

“The Coalition and Iraqi Air Force routinely conduct strikes throughout Western Mosul targeting Isis fighters and other military targets,” he added.

“Due to the relative proximity of the Coalition strikes to the vague location of alleged of civilian casualties Combined Joint Task Force – Operation Inherent Resolve (CJTF-OIR) will further assess this allegation.”

The spokesperson said all reports of civilian casualties are assessed and forces “work diligently to be precise” with targeting in accordance with international law.

The official total for civilians confirmed killed in US-led coalition air strikes stands at 188, although monitors say the real figure is far higher and a number of investigations are underway.

In pictures: Mosul offensive Show all 40 1 /40 In pictures: Mosul offensive In pictures: Mosul offensive A doctor carries an Iraqi newborn baby at a hospital in Mosul, Iraq July 18, 2017. Reuters In pictures: Mosul offensive Iraqi girls play at a yard of a school in Mosul, Iraq July 18, 2017alal Reuters In pictures: Mosul offensive A woman on crutches who is a relative of men accused of being Islamic State militants is seen at a camp in Bartella, east of Mosul, Iraq July 15, 2017. Picture taken July 15, 2017. Reuters In pictures: Mosul offensive A displaced girl, who fled from home carries a doll at Hamam al-Alil camp south of Mosul, Iraq July 13, 2017. Reuters In pictures: Mosul offensive Iraqi federal police members and civilians celebrate in the Old City of Mosul on 9 July 2017 after the government's announcement of the "liberation" of the embattled city. Iraqi Prime Minister Haider al-Abadi's office said he was in "liberated" Mosul to congratulate "the heroic fighters and the Iraqi people on the achievement of the major victory" AFP/Getty Images In pictures: Mosul offensive A picture taken on 9 July 2017, shows a general view of the destruction in Mosul's Old City. Iraq will announce imminently a final victory in the nearly nine-month offensive to retake Mosul from jihadists, a US general said Saturday, as celebrations broke out among police forces in the city. AFP In pictures: Mosul offensive Members of the Iraqi federal police raise the victory gesture as they ride on a humvee while advancing through the Old City of Mosul on 28 June 2017, as the offensive continues to retake the last district held by Islamic State (IS) group fighters. AFP/Getty Images In pictures: Mosul offensive Smoke billows as Iraqi forces advance through the Old City of Mosul on 26 June 2017, during the ongoing offensive to retake the last district held by the Islamic State (IS) group. AFP/Getty Images In pictures: Mosul offensive An Iraqi man wearing the green scarf of the Shi'ite faith kisses an Iraqi Army soldier on safely reaching the Iraqi forces position as Iraqi civilians flee the Old City of west Mosul where heavy fighting continues on 23 June 2017. Iraqi forces continue to encounter stiff resistance with improvised explosive devices, car bombs, heavy mortar fire and snipers hampering their advance. Getty Images In pictures: Mosul offensive A picture taken from the inside of an Iraqi forces armoured vehicle shows residents walking through a damaged street as troops advance towards Mosul's Old City on 18 June 2017, during the ongoing offensive to retake the last district still held by the Islamic State (IS) group. Military commanders told AFP the assault had begun at dawn after overnight air strikes by the US-led coalition backing Iraqi forces. They said the jihadists were putting up fierce resistance. AFP/Getty Images In pictures: Mosul offensive Iraqi Army soldiers advance in a destroyed street after an Iraqi forces airstrike targeted an Islamic State sniper position 17 June 2017 in al-Shifa, the last district of west Mosul under Islamic State control. IS snipers, as well as car and suicide bomb attacks continue to hinder the Iraqi forces efforts to retake the final district. A series of airstrikes by Iraqi helicopter gunships attempted to hit multiple Islamic State sniper positions in al-Shifa. Getty Images In pictures: Mosul offensive An Iraqi soldier frisks a displaced Iraqi man at a temporary camp in the compound of the closed Nineveh International Hotel in Mosul on 16 June 2017 which was recovered by Iraqi troops from Islamic State group fighters earlier in the year. A screening centre set up in the compound's fairgrounds sees a constant stream of Iraqis fleeing the battle for Mosul, awaiting their turn to be checked by the Iraqi forces who are searching for suspected Islamic State (IS) group members. The small fairground lies at the end of a pontoon bridge across the Tigris recently opened to civilians that is the only physical link between the two banks of the river. AFP/Getty Images In pictures: Mosul offensive Iraqis staying at the al-Khazir camp swim in a river near the camp for internally displaced people, located between Arbil and Mosul on 11 June 2017. AFP/Getty Images In pictures: Mosul offensive Iraqi government forces drive on a road leading to Tal Afar on 9 June 2017, during ongoing battles to retake the city from Islamic State (IS) group fighters. AFP/Getty Images In pictures: Mosul offensive An Iraqi policeman carries a poster bearing an image of Mosul's iconic leaning minaret, known as the "Hadba" (Hunchback), on 22 June 2017. AFP/Getty Images In pictures: Mosul offensive Iraqis stand in line to receive food aid in western Mosul's Zanjili neighbourhood on 7 June 2017, during ongoing battles as Iraqi forces try to retake the city from Islamic State (IS) group fighters. Living conditions in Mosul have again deteriorated since the start of the Iraqi government's offensive on the city in October in which they retook a large part of the west of the city. AFP/Getty Images In pictures: Mosul offensive Displaced Iraqis carry lightbulbs and sacks as they evacuate from western Mosul's Zanjili neighbourhood as government forces advance in the area during their ongoing battle against Islamic State (IS) group fighters on 13 May 2017 AFP/Getty Images In pictures: Mosul offensive A member of the Iraqi Counter-Terrorism Service (CTS) flashes the victory gesture as he patrols in western Mosul's al-Islah al-Zaraye neighbourhood on 13 May 2017 AFP/Getty Images In pictures: Mosul offensive Iraqi army soldiers from the 9th armoured division on a truck flash the sign of victory as they drive back from Mosul to the town of Qaraqosh (also known as Hamdaniya) Getty In pictures: Mosul offensive Members of Iraqi forces flash the sign of victory on their vehicle as they advance towards Hammam al-Alil area south of Mosul Getty In pictures: Mosul offensive A member of Iraqi security forces gestures in Hammam al-Alil, south of Mosul, Iraq Reuters In pictures: Mosul offensive Iraqi children, one flashing the sign of victory, greet Iraqi army's soldiers from the 9th armoured division in the area of Ali Rash, adjacent to the eastern Al-Intissar neighbourhood of Mosul Getty In pictures: Mosul offensive Peshmerga forces look at a tunnel used by Islamic State militants near the town of Bashiqa, east of Mosul, during an operation to attack Islamic State militants in Mosul, Iraq Reuters In pictures: Mosul offensive An Iraqi soldier takes a photograph with his phone as his comrade stands next to a detained man, whom the Iraqi army soldiers accused of being an Islamic State fighter, who was fleeing with his family in the Intisar disrict of eastern Mosul, Iraq Reuters In pictures: Mosul offensive Iranian Kurdish female members of the Freedom Party of Kurdistan (PAK) hold a position in an area near the town of Bashiqa, some 25 kilometres north east of Mosul Getty In pictures: Mosul offensive Iraqi families, who fled their homes in Hamam al-Alil, gather on the outskirts of their town Getty In pictures: Mosul offensive Displaced people walk past a checkpoint near Qayara, south of Mosul, Iraq AP In pictures: Mosul offensive Iraqi families who were displaced by the ongoing operation by Iraqi forces against jihadists of the Islamic State group to retake the city of Mosul, are seen gathering in an area near Qayyarah In pictures: Mosul offensive A boy who just fled Abu Jarbuah village is seen with his family at a Kurdish Peshmerga position between two front lines near Bashiqa, east of Mosul, Iraq Reuters In pictures: Mosul offensive An Iraqi child eats a pomegranate upon the arrival of Iraqi forces in the village of Umm Mahahir, south of Mosul Getty In pictures: Mosul offensive People who just fled Abu Jarbuah village sit as they eat at a Kurdish Peshmerga position between two front lines near Bashiqa, east of Mosul, Iraq Reuters In pictures: Mosul offensive A couple who just fled Abu Jarbuah village are escorted by Kurdish Peshmerga soldiers Reuters In pictures: Mosul offensive Women carry a boy over a wall as civilians flee their houses in the village of Tob Zawa, Iraq AP In pictures: Mosul offensive An Iraqi soldier and a civilian ride a motorbike as smoke rises behind them, on the road between Qayyarah and Mosul Getty In pictures: Mosul offensive A member of Iraqi forces, wearing a skull mask, waits at a checkpoint for people fleeing the main hub city of Mosul Getty In pictures: Mosul offensive An Iraqi soldier sits at a checkpoint in an area near Qayyarah Getty In pictures: Mosul offensive Iraqi men prepare food portions for Iraqi forces deployed in areas south of Mosul Getty In pictures: Mosul offensive Iraqi forces celebrate upon the arrival of vehicles bringing food to them Getty In pictures: Mosul offensive Iraqi childen smoke cigarettes upon the arrival of Iraqi forces in the village of Umm Mahahir, south of Mosul Getty In pictures: Mosul offensive A member of Iraqi forces distributes drinks to children in the village of Umm Mahahir, south of Mosul Getty

The UN has warned the Iraqi government and its foreign supporters of the risks posed to families trapped inside Isis-held parts of Mosul.

Iraqi troops, Kurdish forces and Shia militias have advanced through much of eastern Mosul, regaining control of key local government buildings and the city’s university on Friday, but areas to the west of the river Tigris remains under Isis control.

Around 1.5 million civilians were living in the city when the operation to retake it began in October, according to UN figures, and 400,000 have now been freed.

But Isis is known to be forcibly displacing families as it retreats to use them as human shields, with an estimated 750,000 people remaining in the more densely populated western part.

Lise Grande, the UN humanitarian coordinator in Iraq, cautioned that civilian deaths and the lack of a proper humanitarian response will fuel Isis, which bases its narrative on a perceived war between Muslims and the West.

“You would expect in a conflict like this that the number of civilian casualties would be around 15 per cent, a high of 20 per cent,” she said.

“What we’re seeing in Mosul is that nearly 50 per cent of all casualties are in fact civilians.

“It’s clear that this is because of direct targeting by combatants. They’re being targeted by Isil. They’re being shot as they try and leave the city and they’re being shot as they try and secure food and other resources.”

Iraqi children flash the sign for victory in the Al-Natsar neighbourhood in the eastern part of the embattled Iraqi city of Mosul (Getty)

A plan by the Iraqi security forces is seeking to limit civilian casualties by banning artillery strikes, urging civilians to remain in their homes and providing humanitarian corridors.

But as the army and its allies close in on Mosul, humanitarian groups are concerned over the looming possibility of a siege and its dire consequences.

“As soon as Daesh [Isis] is defeated, there are a lot of people who need to get back home, to get back to their lives,” Ms Grande said. “If they don’t, the conditions which led to the rise of Isis will continue to be there.”

The American military hailed the success of Iraqi forces raising their flag over the Nineveh Governorate buildings retaking part of the Mosul University campus and a strategic third bridge on Friday.

Thick clouds of black smoke rose from the middle of the sprawling university complex as clashes continued on Saturday, with volleys of sniper and mortar fire targeting the advancing Iraqi forces from classrooms, dormitories and behind trees.

Operation Inherent Resolve spokesman Colonel John Dorrian said: “Work still needs to be done but Isis’ days in Mosul are quickly coming to an end.”

That assessment is not shared by the vast majority of security analysts, who foresee a gruelling battle lasting for months at least as Isis digs into the city under the cover of the civilians it will prevent leaving.

Iraqi rapid response forces ride on an armoured vehicle during a battle with Isis militants east of Mosul, Iraq, 14 January 2017 (Reuters)

The group has honed its guerrilla warfare techniques even while losing previous strongholds including Fallujah in Iraq and Jarabulus in Syria, rigging deserted buildings and roads with explosives as they withdraw and sending suicide bombers into enemy lines.

Residents told how jihadis forced them out of their homes to use them as sniper positions, knocking through walls so they could move to safety between buildings after being spotted by Iraqi forces.

“Then there is bombardment to destroy the house, to destroy the sniper position,” one man told Reuters. “But the sniper will pop up again here or there.”

Isis fighters overran Mosul in the summer of 2014, with leader Abu Bakr al-Baghdadi using the city’s Grand Mosque to declare his “caliphate” after a rapid advance across Iraq and Syria.

Access to the city's central bank, a large taxable civilian population and nearby oilfields quickly made Isis the world's wealthiest terrorist group.

Mosul is now the last city Isis controls in Iraq, while in Syria it continues to battle against government forces, Kurds and opposing rebels on several fronts.