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 the Islamic State group.
Tens of thousands of civilians escaped the city, just 50 kilometres (30 miles) 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 of 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 government offensive against the IS bastion 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, that houses 1,800 people but has only one latrine for women.