Fears have mounted for people trapped in one of Gaza's main hospitals after Israeli troops raided the facility and health authorities in Gaza said several patients had died there from a lack of oxygen.

The ministry said that at least 120 patients and five medical teams were stuck without water, food and electricity in the Nasser Hospital in Gaza's main southern city of Khan Younis.

In recent days, intense fighting has raged around the hospital — one of the Palestinian territory's last remaining major medical facilities that remains operational.

Troops entered the hospital on Thursday, acting on what the military said was "credible intelligence" that hostages seized in Hamas' unprecedented October 7 attack had been held there and that the bodies of some may still be inside.

The army said it had arrested 20 people, seized weapons and retrieved "medications with the names of Israeli hostages" in the hospital.

'Hospitals deserve safety'

A witness, who declined to be named for safety reasons, told AFP the Israeli forces had shot "at anyone who moved inside the hospital".

Gaza's health ministry also said power was cut off and the generators had stopped after the raid, leading to the deaths of five patients.

It said it held Israel "responsible... considering that the complex is now under its full control".

The Israeli army insisted it had made every effort to keep the hospital supplied with power. "Troops worked to repair the generator while... special forces brought in an alternative generator," it said.

But the World Health Organization on Friday slammed the Israeli operation, with spokesperson Tarik Jasarevic telling reporters that "more degradation to the hospital means more lives being lost".

"Patients, health workers, and civilians who are seeking refuge in hospitals deserve safety and not a burial in those places of healing."

'Killing us slowly'

Doctors Without Borders said its medics had been forced to flee and leave patients behind, with one employee unaccounted for and another detained by Israeli forces.

The UN Human Rights Office said Israel's raid on the Nasser Hospital appeared to be "part of a pattern of attacks by Israeli forces striking essential life-saving civilian infrastructure in Gaza, especially hospitals".

Around 1.4 million displaced civilians are trapped in the town of Rafah, after taking refuge in a makeshift encampment hard by the Egyptian border with dwindling supplies.

"They are killing us slowly," said displaced Palestinian Mohammad Yaghi.

"We are dying slowly due to the scarcity of resources and the lack of medications and treatments."