GAZA CITY - Gaza’s heathcare system is “collapsing” and overflowing hospitals are just “days away” from completely running out of supplies amid the most ferocious Israeli bombardment ever recorded, Palestinian officials have warned.

Intensive care units (ICUs) across the tiny enclave are beyond capacity, forcing doctors to switch off life-support machines for patients deemed “hopeless cases”. They are doing this to make way for the “unprecedented” influx of newly wounded, Gaza’s deputy health minister has said.

“In our religion and ethics, we shouldn’t do this, but we have no choice,” Dr Yusuf Abu al-Reesh added.

Israel imposed a “total siege” on the tiny enclave after militants belonging to Hamas, the group that controls Gaza, launched a surprise deadly attack on Saturday, killing hundreds of people and taking dozens of people, including Britons, hostage.

Rights groups have warned that the decision to impose a siege on the enclave, which is home to more than 2 million people, constitutes collective punishment and is a violation of international law.

However, Israel’s energy minister, Israel Katz, doubled down on Thursday, saying that nothing would be allowed into Gaza until the hostages were released. The Israeli military, meanwhile, said it was ramping up its heaviest bombardment of the strip. More than 1,500 Palestinians have been killed in the onslaught, half of them women and children. More than 6,600 have been injured.

The combination is creating a “humanitarian catastrophe”, United Nations officials have warned. As the wounded poured in, Gaza’s health ministry officials said that hospitals, including al-Shifa, the largest in the enclave, had just “days left of supplies”.

Stocks of vital medicines for emergency departments, such as fluids, bandages and surgical instruments, are said to be running out. Water is in such short supply that doctors at al-Shifa have resorted to using an old well.

“We expanded the hospital by 50 per cent, but even that is full, and we are treating people under a tent in the street,” said deputy health minister Dr Abu al-Reesh from the medical complex in the heart of Gaza City, with desperation in his voice. He shared photos of children, drenched in blood, being treated four to a stretcher on the floor.

“There are no places in the ICU. So for the first time, we have to switch off ICU machines for cases which the doctors believe are hopeless, to make space for those who might have a chance of surviving,” he told The Independent. “We are collapsing.”

The United Nations’ Palestinian refugee aid agency, UNRWA, is meanwhile frantically negotiating with countries around the world to secure a humanitarian corridor. The UN is currently sheltering 220,000 displaced people in 98 of its schools, but their water supply will run out in a few days. Terrified families in Gaza told The Independent on Thursday that they had received leaflets dropped from Israeli aircraft telling them to evacuate, but they didn't know where to go.

“The airstrikes are so heavy they feel like heart attacks,” said 21-year-old Sara, a student who was sheltering with five different displaced families.

And the war, which has already claimed a total of at least 2,700 lives, is expected to escalate.

Tamara al-Rifae, a UNRWA spokesperson, said that with Israeli doubling down on its siege, “All eyes are now on the passage through Rafah to Egypt.”

“That is the only way for aid convoys and personnel to go in,” she continued. “Our highest priority is to find a way for humanitarian personnel and supplies to safely enter Gaza. This is a call for humanitarian access.”

But Egypt’s foreign ministry said on Thursday that airstrikes have prevented Rafah from operating. Egypt has tried unsuccessfully to convince Israel and the United States to allow the delivery of aid and fuel through the crossing.

Gaza was already short on supplies before the latest conflict erupted, as it has been subject to a 16-year siege imposed by Israel and Egypt after Hamas seized control of the strip.

Israel has mobilised 360,000 reservists and appears increasingly likely to launch a ground offensive into Gaza, with its government under intense public pressure to topple Hamas, which has ruled the territory since 2007 and remained firmly in control through four previous wars. Defence officials said on Thursday that they would keep bombing Gaza until “Hamas is wiped from the earth”. The air force said it had dropped more than 6,000 bombs on Gaza to date.

The Israeli military said that more than 1,200 people, including 155 soldiers, had been killed in Israel, a staggering toll on a scale unseen since the 1973 war with Egypt and Syria that lasted weeks.