An Iraqi man in the rubble of destroyed houses in Mosul's al-Jadida area on March 26, 2017, after air strikes which reportedly killed civilians

Iraqi civil defence forces and volunteers removed bodies from the rubble of houses on Sunday in a west Mosul area where air strikes reportedly took a devastating toll on civilians.

Hundreds of thousands of civilians are still trapped, caught between advancing Iraqi forces and the Islamic State group jihadists that they are fighting to defeat.

The battle for Mosul

Iraqi officials and witnesses said air strikes killed civilians in the Mosul al-Jadida area in recent days, but the number of victims -- said by some to number in the hundreds -- could not be independently confirmed.

An AFP photographer saw civil defence personnel and volunteers digging through the remains of houses to recover the dead in Mosul al-Jadida, where at least six homes were completely destroyed.

The remains of 12 people -- among them women and children -- were placed in blue plastic body bags.

An Iraqi counter terrorism forces member in Mosul's al-Jadida area on March 26, 2017, following air strikes which reportedly killed civilians

A 45-year-old man who wept as he spoke said he was living with more than 20 relatives in one of the houses that was destroyed.

The man, who did not want to be identified, survived because he was away at the time, but said he was told that an air strike targeted the house where IS had positioned two snipers on the roof.

Several senior Iraqi military officers visited Mosul al-Jadida on Sunday and asked people what had happened, the AFP photographer said.

Brigadier General Yahya Rasool, the spokesman for the Joint Operations Command, said Iraq is investigating reports of civilian deaths in west Mosul.

- Coalition potentially responsible -

"The defence ministry opened an investigation into this issue," Rasool said.

The US-led coalition against IS has indicated that it may have been responsible for at least some of the civilian deaths, and said it is also conducting an investigation.

"An initial review of strike data... indicates that, at the request of the Iraqi security forces, the coalition struck (IS) fighters and equipment, March 17, in west Mosul at the location corresponding to allegations of civilian casualties," it said in a statement on Saturday.

But that only addresses one day, while Iraqi officials referred to strikes carried out over several.

On Sunday, US Central Command chief General Joseph Votel called recent civilian deaths in Mosul a "terrible tragedy".

"We are investigating the incident to determine exactly what happened and will continue to take extraordinary measures to avoid harming civilians," he said in a statement.

Snipers from the Iraqi forces man their post at the frontline of the Old City of Mosul on March 25, 2017

At the beginning of this month the international alliance had said that "it is more likely than not, at least 220 civilians have been unintentionally killed by coalition strikes", and other incidents were still under investigation.

Two witnesses who have now fled the city said that a building with around 170 people inside was destroyed in Mosul al-Jadida.

Iraqi forces drive down a street on the frontline of the Old City of Mosul on March 25, 2017

One of them said that IS snipers had fired on Iraqi forces, after which an aircraft targeted them with a missile.

An Iraqi brigadier general said that 27 residential buildings had been damaged by multiple days of strikes in west Mosul, and some were completely destroyed.

- Jihadists using human shields -

Some officials from Nineveh province, of which Mosul is the capital, have put the death toll from the strikes in the hundreds, but the number of victims is unclear.

Following the raids, the United Nations called for "everything possible" to be done to protect civilians in Mosul.

"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," said Lise Grande, the UN's humanitarian coordinator for Iraq.

Rasool, meanwhile, said Iraqi forces were seeking to target jihadists using civilians as human shields.

IS "began to use citizens as human shields, and we are trying to target them with... snipers to eliminate them," he said.

Iraqi forces are relying on "light and medium weapons, among them sniper (rifles), to hunt for Daesh members" located among civilians, Rasool said, using an Arabic acronym for IS.

However, Iraqi forces have also frequently fired mortar rounds and unguided rockets during the battle for west Mosul -- weapons that pose a much greater risk to residents where fighting is taking place.

Rasool accused IS of gathering civilians together and blowing up vehicles nearby to make it look like "Iraqi forces... are targeting innocent civilians".

According to Iraqi authorities, more than 200,000 people have fled west Mosul since the operation to retake the area began on February 19.

However, the UN has said that around 600,000 are still inside the city.