Aid workers scrambled Sunday to cope with a massive influx of Iraqi civilians who fled Fallujah after government forces retook much of the city from Daesh.
Tens of thousands of civilians escaped the city, just 50 kilometres west of Baghdad, on the back of a major advance that saw Iraqi forces thrust into central Fallujah in recent days.
The humanitarian community has been struggling to cope, with thousands of people already suffering from hunger and trauma now stranded in the scorching summer heat with no shelter.
"The estimated total number displaced from Fallujah in just the last three days is now at a staggering 30,000 people," the Norwegian Refugee Council said.
The UN refugee agency (UNHCR) said up to 84,000 people had been forced to flee their homes since the start of the offensive nearly a month ago.
"Agencies are scrambling to respond to the rapidly evolving situation -- and we are bracing ourselves for another large exodus in the next few days as we estimate that thousands more people remain trapped in Fallujah," the UNHCR said.
"We implore the Iraqi government to take charge of this humanitarian disaster unfolding on our watch," NRC's Iraq director Nasr Muflahi said.
NRC said it could no longer provide the required assistance, with water rations drying up fast.
It cited the case of a newly opened camp in Amriyat Al Fallujah, south of Fallujah, which houses 1,800 people but has only one latrine for women.
"We need the Iraqi government to take a leading role in providing for the needs of the most vulnerable civilians who have endured months of trauma and terror," Muflahi said.
An Iraqi aid worker employed by the government at a camp in Amriyat Al Fallujah said the resources were inadequate to deal with the scope of the crisis.
"Four hundred families have reached my camp in the last four days, they don't have anything," said the camp manager, speaking on condition of anonymity.
"We were shocked by the number of displaced people and we weren't prepared to receive them," he said.
"We secured tents for some of them but the rest, including women and children, are sleeping on the ground under the sun," he said. "Their situation is a tragedy."
The temperature in Baghdad has been hovering above 40 degrees Celsius (104 Fahrenheit) and it often gets hotter in Anbar province, where inhabited areas along the Euphrates River are flanked by desert.
Prime Minister Haider Al Abadi has promised to support the displaced.