One-third of hospitals in Gaza and nearly two-thirds of primary health care clinics have had to shut due to damage or lack of fuel, the United Nations (UN) has said.
The UN agency for Palestinian refugees (UNRWA) warned it would have to halt operations on Wednesday night due to dwindling fuel supplies.
A lack of resources and masses of wounded have made hospital treatment difficult as Israeli jets continue to strike the territory, where 2.3 million people live.
Tom White, director of the UNRWA, said the “main concern” is that Gaza will run out of fuel.
“We really need to find a solution to the fuel situation, otherwise our aid operation will come to a stop. People will not have access to clean drinking water and hospitals will be closing,” he told CNN.
“Even if convoys come into Gaza, we won’t have the fuel in our trucks to collect and distribute that aid.”
Following a blockade of aid, Israel has allowed a small number of trucks to cross the border from Egypt into Gaza but continued to bar fuel – needed to power hospital generators – to prevent Hamas from seizing it.
Another 20 trucks crossed the Rafah border late on Tuesday, but UN agencies said more than 20 times as much was needed for the population, who depended on aid even in peacetime.
Pope Francis, who said he is “always thinking about the grave situation in Palestine and Israel”, has renewed his calls for help to reach those in need.
“I encourage the release of hostages and the entry of humanitarian aid into Gaza,” he said during his weekly audience on Wednesday.
On Friday, he is expected to lead special prayers for peace in St Peter’s Basilica, in what he said would be a “day of fasting, prayers and penance”.
It follows international calls, led by the US and Russia, for a pause in fighting to allow aid into Gaza.
Washington argued for short pauses to allow aid in, while Russia wants a wider truce.
So far, Israel has resisted both, arguing that Hamas would only take advantage and create new threats to its civilians.
In addition to a lack of fuel, doctors have warned patients are showing signs of disease caused by overcrowding and poor sanitation.
Wounded individuals are laid on the ground without even simple medical aid, while others wait for days for surgery because there are so many critical cases, the Hamas-run health ministry said.
A total of 704 Palestinians, including 305 children, were killed on Tuesday, the health ministry added.
This is the highest number reported in a single day since the conflict began nearly three weeks ago, according to the UN Office for the Coordination of Humanitarian Affairs.
The UN also says more than 5,000 people have been killed in Gaza since 7 October.
In Israel, more than 1,400 people have been killed due to the conflict – mostly civilians murdered during the initial Hamas attack, according to the Israeli government.
Hamas is also holding more than 200 people hostage that it captured and brought back to Gaza.