Gaza - Israel's unrelenting assault on Gaza continued into its fifth week with no sign of slowing Saturday, as US Secretary of State Antony Blinken met Arab foreign ministers in search of a diplomatic opening to ease the crisis.

Washington's top envoy arrived in Jordan for talks with five of his counterparts one day after Israel's Prime Minister Benjamin Netanyahu rebuffed his call for a "humanitarian pause" to allow aid into Gaza.

The Israeli army said its troops had launched an operation in southern Gaza overnight, after deadly strikes hit an ambulance convoy and a school-turned-refugee shelter in the besieged Palestinian territory.

Israeli forces have encircled Gaza's largest city, purportedly trying to crush Hamas in retaliation for October 7 raids into Israel that officials say killed around 1,400 people, mostly civilians.

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On Saturday, the Israeli military said it had come under attack several times from Hamas "tunnel shafts and military compounds" in northern Gaza and had killed many "terrorists" and destroyed three observation posts. Hamas said it had hit an Israeli convoy with mortars.

The health ministry in Gaza says more than 9,488 Palestinians, mostly women and children, have been killed in Israeli strikes and the intensifying ground campaign.

The ministry said at least 12 people had been killed when Israel struck a United Nations school where thousands of displaced Palestinians were sheltering.

Separately, at the Osama bin Zaid Boys School north of Gaza City, AFP saw the aftermath of what Hamas authorities said was Israeli tank shelling that killed 20 people.

Ambulance teams rushed into the debris-littered building to aid the wounded and remove the dead.

Stunned onlookers wept and wandered the scene with their hands clasped on their heads in horror.

A long row of washing still hung from windows on the building's first story, evidence the school had become a temporary home for some of the hundreds of thousands displaced by the war.

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The Israeli military describes Gaza City as "the center of the Hamas terror organization" and says it is targeting militants, weapons stores, tunnel complexes, and command centers.

Overnight, Israeli ground forces launched "a targeted raid" to map tunnels and clear explosive traps in southern Gaza, where it has struck before but rarely sent in troops, the military said.

"The troops encountered a terrorist cell exiting a tunnel shaft. In response, the troops fired shells toward the terrorists and killed them," it said.

Israel says it has struck 12,000 targets across the Palestinian territory since October 7, one of the fiercest bombing campaigns in recent memory.

The army on Saturday sent text messages to Gazans saying the territory's main north-south road would be open for three hours in the afternoon so people can evacuate.

A key focus of his Blinken's Israel visit on Friday was to convince Prime Minister Benjamin Netanyahu to enact "humanitarian pauses," which the United States believes could help secure the release of roughly 240 hostages thought to be in Hamas captivity, and to allow aid to be distributed to Gaza's beleaguered population.

Netanyahu said later, however, that he would not agree to a "temporary truce" with Hamas until the Islamist group releases the hostages.

In Gaza City, an Israeli strike on Friday hit an ambulance convoy near the territory's largest hospital Al-Shifa, killing 15 people, according to the Palestinian Red Crescent and the Gaza health ministry.

Israel's military said it had targeted an ambulance used by a "Hamas terrorist cell" and had "neutralized" those inside.

"We emphasise that this area in Gaza is a war zone. Civilians are repeatedly called upon to evacuate southward for their own safety," the army said.

An AFP journalist saw multiple bodies beside the blood-splattered Palestinian Red Crescent vehicle.

A child was carried away and a dead horse lay nearby, still tethered to a cart.

The Red Crescent said a convoy of five vehicles had been destined for the Rafah border crossing with Egypt, when they were struck multiple times.

One vehicle had been transporting a 35-year-old woman with shrapnel wounds.

World Health Organization chief Tedros Adhanom Ghebreyesus said he was "utterly shocked" by the strike.

"We reiterate: patients, health workers, facilities and ambulances must be protected at all times. Always," he said.

A senior White House official said Hamas had tried to use a US-brokered deal opening the Egyptian border crossing to get its cadres out.

Hamas provided a list of wounded Palestinians for evacuation with one-third of the names those of Hamas members and fighters, the official said.

"That was just unacceptable to Egypt, to us, to Israel," the official added.

Egypt's health ministry said just 17 wounded Palestinians were evacuated for treatment in Egyptian hospitals Friday instead of the 28 originally planned because of the "events" at Al-Shifa.

Blinken began the day in Amman by holding talks with Prime Minister and Foreign Minister Mohammed bin Abdulrahman al-Thani of Qatar, a mediator in the conflict.

He is also scheduled to meet the foreign ministers of Jordan, Egypt, Saudi Arabia, and the United Arab Emirates.

The talks come amid mounting Arab anger over the civilian death toll from war, and increasing fears that the conflict could spread.

Washington has deployed a powerful fleet in the eastern Mediterranean in a show of force against Hezbollah, the Iranian-backed faction in Lebanon, but border clashes continue.

The Israeli military said Saturday it had struck "two terrorist cells" and a Hezbollah post in response to attempted firing from Lebanon.

Saturday's six-nation talks are also likely to touch on the question of Gaza's future beyond the war.

The United States has renewed calls for the creation of a Palestinian state, but few expect success now after decades of failed international efforts to find a "two-state solution."

Netanyahu has spent decades opposing that vision.

The United States has also urged the Palestinian Authority, which ceded power in Gaza to Hamas more than 15 years ago, to retake control. A representative of the Palestinian Authority led by president Mahmud Abbas will also attend the meeting in Amman.