European Union leaders called Thursday for "humanitarian corridors and pauses" to get aid into Gaza as the United Nations warned "nowhere" in the territory is safe from Israel's retaliation for bloody Hamas attacks.

Hamas's armed wing said Israeli strikes have killed almost 50 of the hostages its militants seized during the October 7 attacks, a claim which AFP could not immediately verify.

The attacks saw throngs of Hamas gunmen pour from Gaza into Israel, killing more than 1,400 people, mostly civilians, and kidnapping 224 more, according to official tallies.

Israel has retaliated with relentless strikes that Gaza's Hamas-run health ministry said have killed more than 7,000 people, also mainly civilians -- a toll expected to rise substantially if Israeli troops massed near the border thrust across.

The joint statement from EU leaders came after hours of negotiations at a summit in Brussels.

The 27-nation bloc has long been split between more pro-Palestinian members such as Ireland and Spain, and staunch backers of Israel including Germany and Austria.

"The European Council expresses its gravest concern for the deteriorating humanitarian situation in Gaza," the statement said.

It "calls for continued, rapid, safe and unhindered humanitarian access and aid to reach those in need through all necessary measures including humanitarian corridors and pauses for humanitarian needs," the statement added.

- 'Nowhere is safe' -

Earlier, the UN humanitarian coordinator for the Palestinian territories, Lynne Hastings, said that despite the Israeli military issuing warnings to people in Gaza City to leave, "advance warnings make no difference".

She said in a statement that when evacuation routes are bombed, "people are left with nothing but impossible choices. Nowhere is safe in Gaza."

The army said it had sent tanks, troops and armoured bulldozers into the enclave in a "targeted raid" on Wednesday night that it said destroyed multiple sites before withdrawing.

Black smoke billowed into the sky after a blast in the grainy night-vision footage the Israeli military released hours after Prime Minister Benjamin Netanyahu declared preparations for a ground war were under way.

The operation in northern Gaza came in "preparation for the next stages of combat", the military said.

The raid came after Netanyahu delivered a nationally televised address to Israelis still grieving and furious after the October 7 attacks, telling them "we are in the midst of a campaign for our existence".

International alarm has increased amid growing shock about the scale of human suffering inside the besieged Palestinian territory where Israel has cut off most water, food, fuel and other basic supplies.

In southern Gaza, a grieving Umm Omar al-Khaldi told AFP how she saw her neighbours being killed in an Israeli strike that reduced the house to rubble, with many feared buried beneath.

"We saw them getting bombarded -- the children got bombarded while their mother was hugging them," the woman said, desperately pleading for help from the outside world.

"Where are the Arabs, where is humanity?" she asked.

Amnesty International called for an immediate ceasefire to ensure "access to life-saving aid for people in Gaza amidst an unprecedented humanitarian catastrophe".

- Surging death toll -

The war's surging death toll is by far the highest since Israel unilaterally withdrew from the coastal enclave in 2005 -- a period that has seen four previous Gaza wars.

Entire neighbourhoods have been razed, surgeons are operating without anaesthetic, and ice-cream trucks have become makeshift morgues.

In chaotic scenes, volunteers and neighbours have clawed, sometimes with their bare hands, through shattered concrete and sand to pull out civilian casualties.

All too often they recover only corpses which have piled up, wrapped in bloodstained white shrouds.

US President Joe Biden, a strong supporter of Israel, has joined the calls for it to "protect innocent civilians" and to follow the "laws of war" as it pursues Hamas.

French President Emmanuel Macron warned Wednesday that "a massive intervention that would put civilian lives at risk would be an error".

And Jordan's King Abdullah II said anger at the suffering could "lead to an explosion" in the Middle East.

- 'Raining down hellfire' -

Netanyahu -- amid the growing calls to temper the ferocious bombing campaign -- said Israel had been "raining down hellfire on Hamas" and killing "thousands of terrorists".

He said his war cabinet and the military would determine the timing of a "ground offensive" with the goal to "eliminate Hamas" and "bring our captives home".

But he stressed that "I will not detail when, how or how many" forces would take part.

Netanyahu also acknowledged for the first time that he would have to explain the security lapses exposed on October 7.

"The fault will be examined and everyone will have to give answers, including me," he said. "But all this will happen later."

Biden stressed that "when this crisis is over, there has to be a vision of what comes next".

He reiterated that Washington supports a two-state solution with independent Israeli and Palestinian states.

"It means a concentrated effort for all the parties -- Israelis, Palestinians, regional partners, global leaders -- to put us on a path toward peace," Biden said.

The war has sparked fears of a regional conflagration if it draws in more of Israel's enemies such as Iran-backed Syria and Hezbollah in Lebanon.

There has also been a rise in attacks on Israel's top ally, which has military bases across the Middle East.

About 2,500 American troops are stationed in Iraq and some 900 in Syria to help fight remnants of the Islamic State jihadist group.

The Pentagon said there were 10 attacks on US and allied forces in Iraq and three in Syria between October 17 and 24, involving a "mix of one-way attack drones and rockets".