"The situation in Gaza is not just a catastrophe, it's apocalyptic... with potential irreversible consequences on Palestinian people," said Bushra Khalidi of Oxfam, another UK-based charity.

"Israel safe zones within Gaza are mirage," she added.

Israel launched a massive military offensive against Gaza after Hamas militants burst across the border into southern Israel on October 7 and, according to Israeli officials, killed about 1,200 people, mostly civilians, and took around 240 hostages.

The health ministry in the Hama-run Gaza says 17,487 people have been killed in the war, which has displaced an estimated 1.9 million of the territory's 2.4 million people and reduced vast areas to rubble.

Only 14 of the 36 hospitals in the Gaza Strip are currently functioning in any capacity, according to UN humanitarian agency OCHA, and little aid is reaching those in need.

"Those who survived the bombardment now face imminent risk of dying of starvation and disease," said Alexandra Saieh of Save the Children.

"Our teams are telling us of maggots being picked from wounds and children undergoing amputations without anaesthetic," lining up by the "hundreds" for a "single toilet" or roaming the streets in search of food, she added.

After a week-long pause in hostilities, during which Hamas exchanged hostages for Palestinians held in Israeli jails, Israel pressed its bombing and ground offensive, vowing to eliminate Hamas.

Its army published a map it said was intended to enable Gazans to "evacuate from specific places for their safety if required".

Hundreds of thousands of civilians have fled northern Gaza seeking shelter in the south, only to report that they are being bombed there too.

"There are simply no safe spaces in Gaza, and we've seen this since the (Israeli) directive... calling on people to flee northern Gaza to the south," said Shaina Low of the Norwegian Refugee Council.

"Israeli directives coercing Palestinians in overcrowded areas in southern Gaza, with no guarantees of safety or return, blatantly violate international humanitarian law."

Sandrine Simon of the Medecins du Monde (Doctors of the World) charity recounted how a colleague was wounded in the southern city of Khan Yunis "when a tank attacked a school where he had taken refuge".

"It took him hours to reach a hospital", where "exhausted" nurses were desperately trying to care for hundreds of patients lying on the floor.

"Gaza's hospital are becoming morgues. That's unacceptable," said Simon.

Doctors Without Borders president Isabelle Defourny told a similar story.

"We are working in Al-Aqsa hospital, receiving an average of 150 to 200 war wounded patients daily... since the first of December."

On one day this week, "they received more dead than wounded patients. The hospital is overflowing, the morgue is overflowing, fuel and medical supplies have reached critically low level," said Defourny.

The situation is also dire at the Nasser hospital in Khan Yunis where "20 percent of the patients arriving... are already dead", she added.

"And among the dead, 70 percent are women and children."

Defourny spoke of "indiscriminate carnage".

"Israel has shown a total disregard for the protection of Gaza's medical facilities," she said.

UN agencies have repeatedly warned of a deteriorating health and food conditions in Gaza, a breakdown of public order if no ceasefire is secured.

The World Food Programme has said the risk of "famine" is high, while the World Health Organization have warned civilisation was collapsing in Gaza.

"Given the living conditions and lack of health care, more people could die from disease than bombings" in Gaza, WHO chief Tedros Adhanom Ghebreyesus said.

He warned of a number of illnesses and diseases, including acute respiratory infections, diarrhoea, skin rashes and chicken pox, that have emerged due to overcrowding and the lack of food, water, basic hygiene and access to medication.

"The situation is eroding the people's dignity as they cannot clean themselves nor clean their children," Chiara Saccardi of Action Against Hunger told the video conference, as she called for a ceasefire in Gaza and the dispatch of urgent aid.

On Friday, Israel's top ally the United States vetoed a UN Security Council resolution that would have called for a ceasefire in Gaza.

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