​Washington: The battle to retake Mosul from the Islamic State is only a couple of days old but already chilling stories of civilian suffering are emerging.

Dispatches from humanitarian aid workers on the ground tell of children dying of thirst or being killed by land mines as they try to flee the battle, which began Sunday. Staff at a Save the Children station in the area said a severely dehydrated baby arrive there on the brink of death.

Other children showed up barefoot after a 36-hour trek along a route dotted with homemade bombs planted by the extremists. A family that lost two children to hidden explosives told aid workers they couldn't retrieve the bodies for fear of another blast.

This misery, humanitarian agencies warn, is likely only the beginning of what's expected to be a protracted fight with a dire toll on civilians who either can't escape or who manage to flee but find no sanctuary in overcrowded camps.

In the past few days, international aid agencies have issued urgent appeals for parties to the conflict to protect the 1.5 million people trapped in Mosul. More than half a million children are among those at risk, according to the United Nations.

"With no clear safe routes out of Mosul, thousands are now in danger of getting caught up in the crossfire," said Aleksandar Milutinovic, the International Rescue Committee's director for Iraq. "Civilians who attempt to escape the city will have little choice but to take their lives into their own hands and pray that they are able to avoid snipers, landmines, booby traps and other explosives."

Refugee agencies say 4 million Iraqis have been displaced and more than 24,000 killed since the Islamic State's rampage through much of north and western Iraq in 2014. While the extremist group has been routed from some key territories, retaking Mosul - Iraq's second-largest city - will be a test for Iraqi security forces eager to redeem themselves after their collapse during the 2014 Islamic State march that took the insurgents almost to the capital, Baghdad.

Some 5000 U.S. forces are now in Iraq, advising and training Iraqi security forces, including on the front line. U.S. air strikes are also helping, including 70 in and around Mosul this month alone, according to the Pentagon.

"As Iraqi security forces push toward Mosul, they are already identifying and working to identify escape routes and communicating also directions to civilians as the offensive proceeds," State Department spokesman Mark Toner said Monday without elaboration.

Stories have emerged of nervous Islamic State fighters barring Mosul residents from leaving as they seek to preserve their narrative of a "caliphate" that was welcomed and defended by locals. Without agreed-upon escape routes for civilians, Iraqi military commanders have asked families to stay put and fly white flags from their homes, a prospect that Save the Children dismissed as impractical in a brutal urban conflict and, worse, an opening for "civilian buildings being turned into military positions and families being used as human shields."

The United Nations shares the concern that ordinary families could be forced into acting as shields for the Islamic State.

"Families are at extreme risk of being caught in crossfire or targeted by snipers," said Stephen O'Brien, the UN's coordinator for humanitarian affairs and emergency relief. "Tens of thousands of Iraqi girls, boys, women and men may be under siege or held as human shields."

Even if families make it out alive, there's little guarantee that they'll find sufficient shelter in seven emergency camps. Aid groups expect more than 200,000 people to flee Mosul in the early stages of the battle, but there are only enough tents for 60,000 right now. Humanitarian workers are bracing for a million-person exodus overall, with the vast majority of those - some 700,000, the UN says - projected to require food, water and medical assistance.

If there's no space in the camps, aid workers say, families are likely to seek shelter in abandoned buildings, schools and mosques around Mosul. UN workers and other responders have positioned mobile teams in hopes of reaching the most vulnerable and containing the humanitarian crisis by offer vaccinations against polio and measles.

The International Rescue Committee, for example, is on standby to send mobile response teams to displaced people on the outskirts of the city; they'll be able to provide $US420 cash to 5000 families, representing about 30,000 people, and another 30,000 will receive essential items and medical attention.

The Rescue Committee also is among the handful of agencies that will monitor the mandatory security screenings of all men and boys over age 14 who leave Mosul; Iraqi and Kurdish authorities imposed the checks to make sure no Islamic State fighters flee among ordinary families.

Thousands already have made their way out of nearby Hawija as coalition forces fight their way toward the city. Aram Shakaram, Save the Children's deputy country director for Iraq, said the flow out of the area - traumatized families arrive starving and near collapse after journeys through explosives-laced mountain trails - is a harbinger of the coming crisis.

"This is just the start and we fear it is going to get much more," Shakaram said. "The conditions for people fleeing Hawija are an early warning sign of what will happen when far greater numbers flee Mosul itself."

TNS