Khan Younis, Gaza Strip - Gaza's health ministry said five patients died Friday due to lack of oxygen at one of the Palestinian territory's few operating hospitals that had been raided by Israeli forces.

"A fifth patient at Nasser hospital was martyred as a result of the stopping of generators that caused a cut in oxygen supply," the ministry said in a statement, raising fears for four other patients admitted at the hospital's intensive care unit and three children in a nursery.

Earlier on Friday, it said four patients in the hospital's intensive care unit had died due to lack of oxygen.

"We hold the Israeli occupation responsible for the lives of patients and staff considering that the complex is now under its full control," it said in an earlier statement released on Friday.

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The Israeli military when contacted by AFP said it was checking the report of fatalities at the hospital.

A witness, who declined to be named out of fear for their safety, said army snipers shot "at anyone who moved inside the hospital" and that "military vehicles surrounding" it also opened fire.

On Thursday, the ministry said hundreds of people, including patients and medical staff, had still been inside the hospital complex.

The Israeli army claimed Thursday it had launched a "precise" operation in the hospital after receiving "credible intelligence" to suggest hostages had been held inside, and that the bodies of hostages may be in the facility.

But later Thursday, the army said it had "not yet found any evidence of this," although forces had found "weapons, grenades, and mortar bombs" at the hospital complex.

For weeks, thousands of people displaced by Israel's brutal assault have taken refuge at the complex.

Medical charity Doctors Without Borders said on Thursday that shelling of the hospital had forced its staff to flee, leaving patients behind.

The horrific reports come as the death toll in Gaza has reached at least 28,775 people.