As Iraqi forces attempt to wrest back control from ISIS, the World Food Program (WFP), the International Organization for Migration (IOM) and the World Health Organization (WHO) joined UNICEF in releasing a statement, saying that a fact-finding mission to displaced persons camps showed safe drinking water, food rations, and hygiene and sanitation assistance are urgently needed.
Around 60,000 people are now living in the temporary camps, facilities that are "overstretched," with little capacity to expand.
The U.N.-led mission found people "sheltering in tents or huddled in whatever shade they could find to escape the searing heat and blowing dust," the statement read.
"Most people fled with just their clothes, and many families had been separated from male members who were undergoing screening. One woman approached the mission team members and asked for help, saying: 'We came with nothing, we have nothing,' which characterizes the situation of thousands of other people in the camps."
As the battle for Falluja intensifies, an estimated 50,000 people, including 20,000 children
, are trapped between opposing fighters, according to the United Nations.
Residents of the city, which has been under siege for months
, have had to cope with "acute" shortages of food, medicine and other basic services, such as water supplies, it added.
Falluja residents: 'Immense' suffering
Falluja, which lies 65 km (40 miles) from the capital Baghdad, has been held by the militant group since 2014, and is the subject of a concerted push to retake ISIS-controlled territory across Iraq and Syria.
The U.N. statement also highlighted the parlous security situation in the region, noting that the front lines are mere miles away from the camps.
"The people of Fallujah have suffered immensely under Da'esh," Jan Kubis, Special Representative of the Secretary-General for Iraq said, using an Arabic acronym for ISIS.
"Many of them are on the move, further risking their lives to escape the terrorist group and the fighting, and are desperately in need of safe shelter. They should not be subjected to further suffering and intimidation."
NGO: ISIS targeting civilians
In addition to life-threatening conditions facing those who make it to the camps, the route out of the city is fraught with danger.
According to the Norwegian Refugee Council (NRC), Falluja residents who try to flee have been shot and killed by militants while attempting to cross the Euphrates River to safety.
One woman who had escaped the city had told the NRC that she had seen a young girl drown in the river. Her family tried to send her and two other children across the river in an open refrigerator, but it sank, the NRC said, citing the woman's account.
"On the third week of the intense fighting over Falluja, we are still receiving dreadful stories from civilians who have risked their lives trying to flee to safety," said Nasr Muflahi, the NRC's country director in Iraq.
"We remain extremely concerned for the lives of civilians trapped in the crossfire both inside Falluja, and on their way trying to escape the bullets and bombs."
Iraqi security forces, with the support of other militia, stormed the first neighborhood in southern Falluja at the weekend after recapturing the district of al Nuaimiya -- 5 kilometers (3.1 miles) from central Falluja.
Separately, Iraqi security forces recaptured the key small town of Saqlawiya, 10 kilometers (6.2 miles) northwest of Falluja, on Saturday. Troops there "raised the national flag over the town's main buildings," Iraq's Joint Operation Command said.
The Iraqi military swept through the streets conducting searches for "hundreds of IEDs" that ISIS planted throughout Saqlawiya, military officials said.
Coalition warplanes carried out an airstrike on ISIS militants as they were trying to escape on a raft on the Euphrates River, south of the city, killing everyone aboard raft, the officials said.
In January 2014, Falluja became the first Iraqi city to fall to ISIS -- dealing a blow to Iraq as well as Western countries battling the terrorist group. Saturday is the first time more than two years Iraqi security forces have come this close to a full takeover, army officials said.