Fighting, fuel shortages and Israeli raids put the Gaza Strip's second-largest hospital completely out of service on Sunday, local and UN health officials said, as Israel battled Hamas militants in the devastated Palestinian enclave.

The latest blow to Gaza's destroyed healthcare sector came as Israel prepared for an assault of the southernmost city Rafah, home now to more than a million mostly displaced Palestinians - a move that the international community, including Israel's backer the United States, has warned would create enormous human suffering.

Israel's air and ground offensive has devastated much of Gaza and forced nearly all of its inhabitants from their homes. Palestinian health authorities say 28,985 people, mostly civilians, have been killed.

Gaza's hospitals have been a focal point of the four-month-old war between Israel and Palestinian militant group Hamas.

The Nasser Hospital in the southern city of Khan Younis went out of action early on Sunday, Gaza health ministry spokesperson Ashraf al-Qidra told Reuters.

It still sheltered scores of patients suffering from war wounds and Gaza's worsening health crisis, but there was no power and not enough staff to treat them all, health officials said.

"It's gone completely out of service. There are only four medical teams - 25 staff - currently caring for patients inside the facility," he said.

Qidra said water supply to the hospital had halted because generators had been out of action for three days, sewage was flooding emergency rooms and the remaining staff had no way of treating intensive care patients.

A lack of oxygen supplies - also a result of having no power - had caused the deaths of at least seven patients, he said.

The Gaza war began when Hamas, which controls Gaza, sent fighters into Israel on Oct. 7, killing 1,200 people, mostly civilians, and seizing 253 hostages, according to Israeli tallies. The conflict has destabilised the entire Middle East as Hamas's military allies - all Iran-backed paramilitary groups - have targeted Israeli and U.S. interests with missiles and drones.

Most of Gaza's hospitals have been put out of action by fighting and lack of fuel, leaving a population of 2.3 million without proper healthcare.

Israel has raided medical facilities alleging that Hamas keeps weapons and hostages in hospitals. Hamas operates across densely-populated Gaza but denies it uses hospitals for cover.

The international community says hospitals, which are protected under international law, must be protected.

The World Health Organization urged Israel to grant its staff access to the hospital, where it said a week-long siege and raids by Israeli forces searching for Hamas militants had stopped them from helping patients.

"Both yesterday and the day before, the @WHO team was not permitted to enter the hospital to assess the conditions of the patients and critical medical needs, despite reaching the hospital compound to deliver fuel," WHO head Tedros Adhanom Ghebreyesus said on social media platform X.

The Israeli military said its special forces were operating in and around Nasser Hospital, and had killed dozens of Palestinian militants and seized a large amount of weapons in fighting across Gaza over the past day.

The military said this week it was hunting for militants in Nasser and had arrested at least 100 suspects on the premises, killed gunmen near the hospital and found weapons inside it.

Strikes kill displaced in Rafah

Israel's assault on Gaza began in the north and has moved south as Palestinians have fled, many crammed into tents around southern cities including Khan Younis and Rafah, the Gaza-Egypt border town which is the only crossing not controlled by Israel.

More than half Gaza's population has been pushed into Rafah and Israeli plans to storm the city have prompted international concern.

Israeli planes carried out attacks on two areas in Rafah on Sunday, including an empty building near the border with Egypt, local residents and Hamas media officials said.

The second of the two strikes hit an open space where displaced people were sheltering, killing six people, local medics said.

Israel's Prime Minister Benjamin Netanyahu, embattled at home over the government's failure to stop the Oct. 7 attack and under pressure to get the remaining hostages released, on Saturday pledged to push on with the military campaign.

Netanyahu has rejected internationally-backed attempts to negotiate a ceasefire as Arab and Western countries call for a lasting solution to the core of the Israeli-Palestinian conflict in the creation of a Palestinian state in the West Bank and Gaza alongside Israel.

His cabinet on Sunday formalised its opposition to what it called the "unilateral recognition" of Palestinian statehood.