Gaza City, Gaza - Gaza's main hospital has been forced to bury scores of dead patients in a mass grave, its director said Tuesday, as US President Joe Biden pressed Israel to protect the complex it has put under siege.

Israeli forces were at the gates of the sprawling Al-Shifa hospital they claim sits atop an underground Hamas command base, but the militants and medical organizations deny the charge, while doctors say thousands of people are stranded inside in horrific conditions.

"There are bodies littered in the hospital complex and there is no longer electricity at the morgues," said Al-Shifa hospital director Mohammad Abu Salmiyah, adding that 179 bodies had been interred so far.

"We were forced to bury them in a mass grave," he said, adding that seven babies and 29 intensive care patients were among those who had died after fuel for the hospital's generator ran out, due to Israel's total blockade.

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A witness said the smell of decomposing bodies was everywhere in the facility, but nighttime fighting and air strikes had been less intense compared to previous nights.

The United Nations believes that thousands, and perhaps more than 10,000 people – patients, staff, and displaced civilians – may be inside and unable to escape because of fierce fighting nearby.

Israel says it is not targeting the hospital, but medical staff have accused its forces of killing those trying to escape, as well as repeatedly firing into the facility itself.

The health ministry in Gaza says Israel's relentless assault in response to the October 7 attack has killed over 11,000 people, also mostly civilians, including close to 5,000 of children. Some 1,200 were killed in the Hamas operation in Israel, while 47 Israeli troops have died since in the Gaza war began.

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Joe Biden called on Israel to use "less intrusive action relative to the hospital", some of his most pointed comments on Israeli operations to date.

"The hospital must be protected," he told reporters, as international outrage builds over the death and suffering the war has inflicted on Gaza civilians.

Israel's top diplomat acknowledged Monday that his nation has "two or three weeks until international pressure really steps up".

Quoted by his spokesperson, Foreign Minister Eli Cohen added that Israel is working to "broaden the window of legitimacy, and the fighting will carry on for as long as necessary."

Biden has so far refused to call for a ceasefire, which prompted Center for Constitutional Rights to launch a lawsuit on behalf of Palestinians who say his administration is enabling genocide.