BAGHDAD - The Iraqi military on Sunday blamed the Islamic State militant group for the killing of dozens of civilians at a house in western Mosul.

A statement by the Joint Operations Command also denied that the house was bombed by airstrikes conducted by coalition aircraft.

A team of experts dispatched to the scene in the al-Jadida area discovered that the walls of the house, which was completely destroyed, had been booby-trapped by IS militants.

The experts also found remains of a large booby-trapped truck beside the house, which could be the reason behind the house collapse, according to the statement.

It said that there was no evidence that the house was hit by an airstrike.

Earlier, media reports said hundreds of civilians were buried under the debris of their houses after heavy air bombardment from the United States-led coalition in the past few days.

On Friday, the United Nations expressed concerns about reports of civilian casualties in Mosul, and urged all sides in the conflict to avoid such casualties.

"We are stunned by this terrible loss of life and wish to express our deepest condolences to many families who have reportedly been impacted by this tragedy," a UN statement quoted Lise Grande, the humanitarian coordinator for Iraq, as saying.

"Nothing in this conflict is more important than protecting civilians. All parties of the conflict 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."

Iraqi Prime Minister Haider al-Abadi, who is also commander-in-chief of the armed forces, announced the start of an offensive on Feb 19 to drive extremist militants out of the western side of Mosul, locally known as the right bank of the Tigris River, which bisects the city.

Late in January, Abadi declared the liberation of Mosul's eastern side after more than 100 days of fighting IS militants.

However, Mosul's heavily-populated western part, with its narrow streets, appears to be a bigger challenge to Iraqi forces.

According to Iraqi authorities, more than 200,000 people have fled west Mosul, but the UN has said that around 600,000 are still inside the city.

Mosul, 400 kilometers north of Iraqi capital Baghdad, was taken over by IS in June 2014, when government forces abandoned their posts and fled, enabling the militants to take control of parts of Iraq's northern and western regions.