Almost a million people in Gaza are without reliable water supplies, electricity is scarce, and more than 50,000 people have been forced to flee their homes.
Adnan Abu Hassna, a spokesman for the UNRWA, told Al Jazeera that his agency needs $60m to cope with the crisis
He said the number of those forced from their homes had exceeded the last Gaza war in 2009. "We will need more shelters and more centres within the coming days."
At a UN-run school visited by Al Jazeera, Ms al-Muqayad, forced to flee her home, said they had not had showered for days.
The school, on the edge of the Beach Refugee Camp in west Gaza, is home to more than 1,470 people in 47 rooms. There are no showers.
"Life here is like prison… No, prison is better," Muqayad said.
Her 10-year-old daughter, Areej, says that she can't sleep in the night because of the bombing. "I pray this will be over and I go to my home. I miss it," she said.