Heavy rain falling on Gaza has added to the hardship of Palestinians, with fears of disease outbreak and flooding as hundreds of thousands of displaced people live in tents in crowded camps.

The United Nations on Wednesday (AEDT) voiced concern about the rain, which will “just add further to the suffering” of people in the Gaza Strip.

“We’ve already got outbreaks of diarrhoeal diseases. We’ve got so much infrastructural damage. We’ve got a lack of clean water,” WHO spokesperson Margaret Harris said.

“We’ve got people very, very crowded together. This is another reason why we are begging for a ceasefire to happen now.”

The WHO said there had been more than 33,500 cases of diarrhoea since mid-October, 16 times the monthly average. Most were among children younger than five.

The UN’s refugee camps, where 580,000 displaced people have sought shelter, are more than nine times over capacity and the overcrowding was posing further health risks, the UN said.

Norwegian Refugee Council spokesperson Ahmed Bayram told Reuters the start of the rainy season could mark “the most difficult week in Gaza since the [military] escalation began.”

“Heavy rains will mean more impeded movement for people and rescue teams,” he said.

“It will make it harder to save people stuck under the rubble, or to bury the dead, all of this amidst ceaseless bombardment and a fuel shortage catastrophe.”

Winter can be cold and wet in the region and the downpour signalled the start of the rainy season.

The situation goes from bad to worse as rain falls on Gaza. Photo: Getty

Hospital digs mass grave

Meanwhile, the horror continues to unfold at Gaza’s largest hospital Al Shifa, where a mass grave has been dug to bury patients who have died under Israeli encirclement.

Israeli forces have surrounded the hospital, in Gaza City, which they say sits atop an underground headquarters of Hamas militants. Hamas denies its fighters are there.

The UN said six premature babies had reportedly died in the past three days as their incubators were unable to function because of there is no electricity.

The Israeli military has reportedly offered to provide incubators to the hospital.

UN Secretary-General António Guterres said he was “deeply disturbed by the horrible situation and dramatic loss of life” reported in Gaza’s medical facilities.

“In the name of humanity, the Secretary-General calls for an immediate humanitarian ceasefire,” a statement said.

Five weeks after Israel swore to destroy Hamas in retaliation for a cross-border assault by militants, the fate of the encircled hospital has become a focus of international alarm including from Israel’s closest ally, the US.

Ashraf Al-Qidra, Gaza’s health ministry spokesman, reached by telephone inside the hospital compound, said about 100 bodies were decomposing inside, with no way to get them out.

Medics in Hamas-run Gaza say more than 11,000 people have been killed in Israeli strikes.

“We are planning to bury them today in a mass grave inside the Al Shifa medical complex. It is going to be very dangerous as we don’t have any cover or protection from the ICRC but we have no other options – the corpses of the martyrs began to decompose,” he told Reuters.

“The men are digging right now as we speak.”

Thirty-six babies are left from the neonatal ward after three died.

Without fuel for generators to power incubators, the babies are being kept warm as best as possible, lined up eight to a bed.

Israel said on Tuesday that it was offering portable, battery-powered incubators so the babies could be moved.

But Qidra said arrangements for such a relocation were yet to be made.

“We have no objection to have the babies being moved to any hospital, in Egypt, the West Bank or even to the occupation (Israeli) hospitals. What we care most about is the wellbeing and the lives of those babies,” he said.

“The occupation is still besieging the hospital and they are firing into the yards from time to time. We still can’t move around but sometimes doctors are taking the risk when they need to attend to patients.”

Israel denies the hospital is under siege and says its forces allow routes for those inside to exit.

Medics and officials inside the hospital say this is not true and those trying to leave have come under fire.

Reuters could not verify the situation independently.

Israel vowed to wipe out Hamas after the militant group’s fighters burst across the fence around the enclave and rampaged through Israeli towns killing civilians on October 7.

Israel says 1200 people were killed and about 240 were dragged back to Gaza as hostages in the deadliest day of its 75-year history.

But its response, including a total siege and constant bombardment of the small densely populated enclave that has killed many thousands of civilians, has alarmed foreign governments.

Israel says Hamas is to blame for harm to civilians because fighters hide among them; Hamas denies this.

Palestinians search for people still trapped under rubble in Gaza. Photo: Getty

Another surgeon, Dr Ahmed El Mokhallalati, told Reuters from Al Shifa hospital that the main risk now was the dead bodies decomposing inside.

“We are sure that all kind of infections will be transmitted from that one. Today we had a little bit of rain… It was really horrible, nobody could even open a window, or just walk around the corridors with a really bad smell,” he said.

“Burying 120 bodies needs a lot of equipment, it can’t be by hand efforts and by single person efforts. It will take hours and hours to be able to bury all these bodies.”

He said that on Monday doctors had performed surgery without any oxygen, which made general anaesthesia impossible.

-with AAP