Israeli raids and fuel shortages have put Gaza's second-largest hospital completely out of service on Sunday, local and UN health officials said, as Israeli forces continue to battle Hamas militants in the devastated Palestinian enclave.

The Nasser Hospital in the southern city of Khan Younis is still sheltering scores of patients amid Gaza's worsening health crisis, but there was no power and not enough staff members to treat everyone, health officials said.

"It's gone completely out of service," Gaza's Health Ministry spokesperson Ashraf al-Qidra was quoted by Reuters as saying.

"There are only four medical teams – 25 staff – currently caring for patients inside the facility," he said.

Al-Qidra said the hospital no longer has water supply because generators have been shut down for three days, sewage was flooding emergency rooms and the remaining staff had no way of treating intensive care patients.

Lack of oxygen supplies – also a result of the power outage – had caused the deaths of at least seven patients, he said.

Gaza's hospitals have been a focal point of the four-month-old conflict between Israel and Hamas. Most medical facilities have been put out of action due to fighting and lack of fuel, leaving a population of 2.3 million without proper access to basic healthcare.

Israel has repeatedly raided medical facilities across Gaza alleging there were used by Hamas to keep weapons and hostages. Hamas operates across the densely-populated Gaza but denies it uses hospitals for cover.

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

The World Health Organization (WHO) 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 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.

(With input from Reuters)