The US-led coalition bombing ISIL positions in Iraq has admitted that it carried out air raids last week at a location in west Mosul where officials and residents say scores of civilians were killed.

The acknowledgement on Saturday came hours after the United Nations said it was "stunned" by the reported deaths of civilians in suspected coalition air raids in Mosul's ISIL-held al-Jadida district on March 17.

"An initial review of strike data ... indicates that the coalition struck [ISIL] fighters and equipment, March 17, in west Mosul at the location corresponding to allegations of civilian casualties," the US military's Combined Joint Task Force said in a statement on Saturday.

The coalition said that it had struck the area "at the request of the Iraqi security forces" and was investigating to determine the facts and the validity of reports of civilian casualties.

Al Jazeera's Hoda Abdel-Hamid, reporting from Erbil in northern Iraq, said it took about a week for the coalition to acknowledge the air raids.

"The response came after intense pressure here in Iraq - probably popular pressure more than government pressure," she said.

"About 200 people are thought to have died in that strike alone," our correspondent added. "These reports of a high toll of civilian casualties were first given by the civilians who actually managed to get out of western Mosul."

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Iraqi officials and witnesses say that air raids in west Mosul have killed hundreds of people in recent days, but the exact number of victims could not be independently confirmed.

Bassma Bassim, the head of the Mosul District Council, said "more than 500" civilians were killed by air raids over the past week alone.

"I have never met so many people with so many martyrs in their families," Bassim said, adding that witnesses are questioning whether civilians are being targeted on purpose.

"I have talked to so many people from the victims' families who confirmed that there are only five or six ISIL fighters in the new Mosul area who freely move in the streets without being targeted. They said only civilians in the area are being targeted."

Nawfal Hammadi, the governor of Nineveh, of which Mosul is the capital, said the coalition had carried out the air raids in al-Jadida.

Hammadi had put the toll at "more than 130 civilians" killed, but later referred to "the burial of hundreds of martyrs under the rubble of the houses in the Mosul al-Jadida area".

Civil defence officials and residents have said many people lay buried in collapsed buildings after air raids against the Islamic State of Iraq and the Levant, (ISIL, also known as ISIS) triggered a big explosion.

Reports on the numbers of civilian casualties have varied but Civil Defence chief Brigadier Mohammed Al-Jawari told reporters on Thursday that rescue teams had recovered 40 bodies from collapsed buildings.

The Speaker of the Iraqi parliament, Salim al-Jabouri, said in a statement: "What's happening in the west part of Mosul is extremely serious and could not be tolerated under any circumstances."

Earlier on Saturday, the UN expressed profound concern over the escalating civilian death toll in the battle to retake Mosul.

"We are stunned by this terrible loss of life," Lise Grande, the humanitarian coordinator for Iraq, said in a statement referring to the March 17 incident.

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Mark Kimmitt, a former US assistant secretary for political and military affairs, told Al Jazeera that while the deaths of civilians were unfortunate, such "incidents happen in combat".

He added: "Coalition forces are doing everything they can, along with Iraqi security forces, to minimise civilian casualties.

"But let's be clear: [ISIL] deliberately kept civilians in this area for this specific purpose."

The US-backed offensive to drive ISIL out of Mosul, now in its sixth month, has recaptured most of the city. The entire eastern side and about half of the west is under Iraqi control.

But advances have stuttered in the past two weeks as fighting enters the narrow alleys of the Old City, home to the al-Nuri Mosque where ISIL group's leader Abu Bakr al-Baghdadi declared a caliphate spanning large areas of Iraq and Syria in 2014.

Al Jazeera's Abdel-Hamid said thousands of civilians are "trapped" inside the Old City and exposed to the intense fighting.

"ISIL fighters have been using snipers on top of the building in the city shooting randomly at any civilians, including children," she said.

"Many children in the hospital near Erbil have known to be specifically targeted by these snipers. We can see a very complicated battle ahead."

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Iraqi government forces have temporarily paused their push to recapture Mosul because of the high rate of civilian casualties, a security forces spokesman said.

"The recent high death toll among civilians inside the Old City forced us to halt operations to review our plans," a Federal Police spokesman said on Saturday.

"It's a time for weighing new offensive plans and tactics. No combat operations are to go on."

The fighters have used civilians as human shields and opened fire on them as they try to escape ISIL-held neighbourhoods, fleeing residents said.

The UN's Grande said civilians were at extreme risk as the fighting in Mosul intensified and all sides must to do their utmost to avoid such casualties.

"International humanitarian law is clear. Parties to the conflict - all parties - 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," she said.

Fleeing residents have described grim living conditions inside the city, saying there is no running water or electricity and no food coming in. Aid agencies say as many as 600,000 civilians remain in the western half of Mosul.

The eastern side of the city was recaptured in a three-month offensive that ended in January, but the west, with its densely populated maze of narrow streets, is thought to pose a greater challenge.