Fighting raged Monday in and around the besieged Gaza Strip's largest hospital complex where Israel said its forces killed and arrested Hamas militants, as Palestinians fled by foot under heavy bombardment.

While the army launched the overnight raid at Gaza City's Al-Shifa hospital, the Israeli government sent the head of its Mossad spy agency to Qatar for renewed talks toward a ceasefire and hostage release deal.

The devastating war since Hamas's October 7 attack on Israel has left roughly half of Gazans -- around 1.1 million people -- experiencing "catastrophic" hunger, a UN-backed food security assessment warned.

The expert report is "exhibit A for the need for an immediate humanitarian ceasefire", said United Nations Secretary-General Antonio Guterres, decrying an "entirely man-made disaster".

"We must act now to prevent the unthinkable, the unacceptable and the unjustifiable," he said.

Gaza's soaring civilian death toll and large-scale destruction have hardened global opposition to Israel's military operation and siege, including accusations of deliberate starvation of Palestinian civilians.

European Union foreign policy chief Josep Borrell said Israel's military campaign had turned long-blockaded Gaza from the world's "greatest open-air prison" into its biggest "open-air graveyard", and that Israel was using famine as a "weapon of war".

Foreign Minister Israel Katz replied that "Israel allows extensive humanitarian aid into Gaza" and accused Borrell of "attacking Israel".

In the latest heavy battle, Israeli forces raided Al-Shifa in an operation the army said targeted senior Hamas militants.

Witnesses reported air strikes and tanks near the complex crowded with thousands of Palestinian patients and displaced people.

AFP images showed black smoke engulfing parts of the city after bombardment, with Palestinians fleeing by foot along rubble-strewn roads as others treated the wounded in the street.

The health ministry in the Hamas-run Gaza Strip said nearby residents had reported dozens of casualties who could not be helped "due to the intensity of gunfire and artillery shelling".

An AFP journalist witnessed air strikes on buildings in the area around Al-Shifa and reported seeing "hundreds of people, mostly children, women, and the elderly, fleeing their homes".

  Hospital raided again 

 The Israeli military, which had asked Gazans to evacuate the area, said 20 militants were killed and dozens of others were detained at the hospital.

The army identified one of the fatalities as Hamas internal security official Fayq al-Mabhouh, saying that "weapons were located in the room adjacent to where he was eliminated."

A Gaza police source confirmed his death and said he was a brigadier general in the force. Relatives said he was also the brother of Mahmoud al-Mabhouh, one of the founders of Hamas's armed wing slain in Dubai in 2010.

Israeli forces previously raided Al-Shifa in November, when ground operations were focused on northern Gaza. In January Israel said it had "completed the dismantling" of Hamas's command structure in the area.

Israel has repeatedly said the complex housed an underground Hamas control base, which the militants have denied.

World Health Organization chief Tedros Adhanom Ghebreyesus said he was "terribly worried" about the renewed fighting around Al-Shifa which was "endangering health workers, patients and civilians".

The bloodiest ever Gaza war broke out after Hamas launched an unprecedented attack on October 7 that resulted in about 1,160 deaths in Israel, mostly civilians, according to an AFP tally based on official Israeli figures.

Militants also seized about 250 hostages, of whom Israel believes 130 remain in Gaza, including 33 who are presumed dead.

Israel has carried out a relentless bombing campaign and ground offensive that Gaza's health ministry says has killed at least 31,726 people, most of them women and children.

  'Nothing to eat' 

 As the fighting flared around Al-Shifa, elsewhere in Gaza City a massive crowd gathered at a UN food distribution centre to collect bags of flour.

"There's nothing to eat or drink. Children are dying," said resident Umm Omar al-Masharwai.

The UN agency for Palestinian refugees, UNRWA, which operates the facility and coordinates nearly all aid to Gaza, has faced funding cuts since Israel accused about a dozen of its employees of involvement in the October 7 attack.

UNRWA chief Philippe Lazzarini said Monday he intended to visit Gaza but had been denied entry by "Israeli authorities", a claim Israel did not immediately comment on.

Jordanian Foreign Minister Ayman Safadi accused Israel of "starving children to death" in its siege of the Gaza Strip, and humanitarian charity Oxfam said Israel was "systematically and deliberately" blocking aid.

Global concern has focussed on Gaza's far-southern city of Rafah, where about 1.5 million Palestinians now live, many of them in crowded shelters and tent cities near the Egyptian border.

Repeated Israeli warnings of a looming ground invasion have raised fears of an even worse humanitarian catastrophe.

  Truce talks 

 Responding to concerns voiced by top ally the United States and other governments, Israeli Prime Minister Benjamin Netanyahu on Sunday reiterated that civilians would be evacuated from Rafah before any ground attack, without detailing where to.

Mediation efforts toward a truce were expected to resume, following a week-long ceasefire in November.

A meeting in Qatar between Israel's Mossad spy chief, David Barnea, Qatari Prime Minister Mohammed bin Abdulrahman Al-Thani and Egyptian officials "is expected to take place today", a source close to the talks said.

It follows the latest proposal submitted by Hamas for a six-week truce, vastly more aid into Gaza and the initial release of about 42 hostages in exchange for Palestinian prisoners held by Israel.

During the proposed truce, Israeli forces would withdraw from "all cities and populated areas" in Gaza, according to a Hamas official.

Netanyahu's office said on Friday that Hamas's new proposal was "unrealistic" but that Israel would send a delegation to Doha.

The White House said US President Joe Biden and Netanyahu spoke on Monday in their first call for over a month, with tensions rising over the war and its impact on civilians.