A massive price tag to rebuild Iraq after Islamic State

More than 3,000 tons cover every acre, and much of the shattered concrete and twisted metal that once made up people's homes and shops is laced with explosives and unexploded ordnance.

The debris field marking the district where the Islamic State group made its last stand extends for nearly 2 and a half miles along the western bank of the Tigris River and is more than a mile wide and throughout, hardly a singly building is left unscathed.

The Old City has the densest wreckage, but nearly every neighborhood in the western half of Mosul has entire blocks in ruins, and all five bridges crossing the Tigris have been disabled by airstrikes.

This is just one corner of the destruction that three years of war wreaked across northern and western Iraq.

The US-led coalition and Iraqi forces defeated IS militants, but the cost of victory is nearly incalculable.

Baghdad estimates $100 billion is needed nationwide to rebuild. Local leaders in Mosul say that amount is needed to rehabilitate their city alone.

So far no one is offering to foot the bill. The United States has told the Iraqis it won't pay for a massive reconstruction drive. Iraq hopes Saudi Arabia and other Gulf countries will step up, and Iran may also take a role.

UN projects are repairing infrastructure in nearly two dozen towns and cities, but funding is a fraction of what will be needed. As a result, much of the rebuilding has come from individual Iraqis using personal savings.

In the meantime, many of those who fled IS or the fighting remain uprooted. While 2.7 million have returned, more than 3 million others cannot and they languish in camps.

Worst hit is Mosul; the UN estimates 40,000 homes there need to be rebuilt or restored, and some 600,000 residents have been unable to return to the city, once home to around 2 million people.

Corruption and bitter sectarian divisions make things even harder. The areas with the worst destruction are largely Sunni, while the Baghdad government is Shiite-dominated. The fear is that if Sunni populations feel they've been abandoned, resentment will feed the next generation of militants.

If Mosul is not rebuilt, "it will result in the rebirth of terrorism," said Abdulsattar al-Habu, the director of Mosul municipality and reconstruction adviser to Nineveh province, where the city is located.

Mosul, overrun by IS in 2014, was declared liberated in July, after a months-long battle that inflicted its greatest destruction on its western sector. An Associated Press investigation found at least 9,000 civilians died in the assault to retake Mosul.

The enormity of the task ahead can be grasped by what has and hasn't happened in Ramadi, which was liberated from IS two years ago. More than 70 per cent of the Anbar provincial capital remains damaged or destroyed, according to the provincial council.

Nearly 8,300 homes almost a third of the houses in the city were destroyed or suffered major damage, according to UN Habitat. Repairs have begun on only three of the five damaged bridges over the Euphrates River.

Three-quarters of the schools remain out of commission.

The Anbar provincial council holds its meetings in a small building down the street from the pile of rubble that was once its offices.