Health officials in Gaza on Tuesday said at least 200 people were killed in an air strike on a hospital compound which sheltered the wounded and displaced from Israeli bombing, prompting condemnation and fury in the Middle East and beyond.
The Hamas-run health ministry claimed that Israel was behind the attack on the Ahil Arab Hospital in Central Gaza but Israel's military blamed a malfunctioning rocket fired by Islamic Jihad militants.
The strike, soon after the UN said at least six were killed in a strike on a nearby UN-run school during Israeli bombardments, escalates the 11-day-old war, which has already claimed thousands of lives on both sides.
It also happened just hours before US President Joe Biden was due to touch down in the Middle East for high stakes talks on the war, which was cancelled as summit host Jordan and the wider region mourned the victims, the White House said.
Biden's visit to Israel was still going ahead.
In chaotic scenes, those injured were taken from the Ahli Arab hospital in ambulances to other medical centres nearby, while medics and civilians covered rows of the dead in white plastic sheets or blankets.
Qatar called it "a brutal massacre" and a "heinous crime against defenceless civilians", with the African Union, World Health Organization and Arab League among those criticising the strike.
In Jordan, protesters tried to storm the Israeli embassy while Hamas's ally, the Iran-backed Hezbollah movement in Lebanon, called for a "day of rage" on Wednesday.
"We were operating in the hospital. There was a strong explosion and the ceiling fell on the operating room." said Ghassan Abu Sittah, a doctor with medical charity Doctors Without Borders (MSF).
He added: "Hospitals are not a target. This bloodshed must stop. Enough is enough."
The Gaza Health Ministry said between 200 and 300 people were killed at the hospital in "occupation (Israeli) strikes" and hundreds more were trapped.
In response, Israel's military said that "a barrage of rockets was fired by terrorists in Gaza, passing in close proximity to Ahli hospital in Gaza at the time it was hit".
"Intelligence from multiple sources we have... indicates that Islamic Jihad is responsible for the failed rocket launch which hit the hospital in Gaza," it added.
Gaza-based Islamic Jihad has claimed to be fighting Israel alongside Hamas, which rules the Palestinian coastal enclave.
Biden's trip comes after Hamas fighters -- under cover of a rocket barrage -- burst through Israel's heavily fortified Gaza border, shooting, mutilating and burning more than 1,400 people on October 7.
Shell-shocked Israel has responded with withering air strikes against targets in Gaza, leaving about 3,000 Gazans dead, the health ministry in Gaza said before the Ahli Arab strike.
Israel has also imposed a crippling siege on the impoverished territory and deployed tens of thousands of troops on the border with Gaza in preparation for a full-scale ground offensive.
It has vowed to destroy Hamas while also seeking to rescue the at least 199 hostages taken into Gaza by Hamas, which has released a video of one of the captives, French-Israeli woman Mia Shem.
Her mother, Keren Shem, made an emotional plea for her safe return. "I am begging the world to bring my baby back home," she told a news conference in Tel Aviv.
Diplomatic bids to free the hostages have gathered pace. Turkey said it was in talks with Hamas to secure their release.
But there were mixed views about how effective Biden could be, with some Palestinians blaming the United States for backing Israel, and even Israelis sceptical.
"We don't believe anymore in politicians," said Omer Nevo, 23. "I don't trust anyone anymore after what has happened here."
Israelis are reeling from the worst attack on civilians in the country's 75-year history, which has sparked a mass mobilisation of reservists and the evacuation of residents from areas near Gaza and Lebanon.
In southern Israel, dozens of mourners gathered for the funeral of five members of the same family killed when militants attacked their kibbutz at Kfar Aza.
All five coffins were draped in Israeli flags.
US Secretary of State Antony Blinken, back in Israel after a whistlestop regional tour, said Biden's visit would be a statement of "solidarity with Israel" and an "ironclad commitment to its security".
Support also came from Germany, whose Chancellor Olaf Scholz was in Tel Aviv.
"The world must stand united behind Israel to defeat Hamas," Israel's Prime Minister Benjamin Netanyahu said, alongside Scholz.
Washington has already sent two aircraft carrier strike groups to the eastern Mediterranean "to deter hostile actions against Israel".
The Pentagon has put 2,000 troops on deployment alert to be able "to respond quickly to the evolving security environment in the Middle East". US media said the troops would cover support roles such as medical assistance and handling explosives.
Israel's arch foe Iran, which backs both Hamas and Lebanon-based Hezbollah militants, has repeatedly warned against a Gaza invasion and Monday raised the spectre of a possible "pre-emptive action" against Israel "by the resistance axis."
Iran's supreme leader Ayatollah Ali Khamenei said Tuesday that "no one can stop" forces opposed to Israel if it keeps up its bombardment of Gaza.
Deadly flare-ups have rocked Israel's northern border with Lebanon.
Israel's army said Tuesday it had killed four militants attempting to infiltrate from Lebanon.
Hezbollah later said five of its fighters were killed "performing jihad", taking the number of its fighters killed in the intensifying border skirmishes to 10.
White House National Security Council spokesman John Kirby was asked on CNN whether US authorities had so far noticed Iran engaging in the conflict in new ways.
"Outside of the rhetoric..., no we haven't," he replied.
'Corpses in the street'
Biden will also try to quietly steer Israeli's military response, as international alarm has grown about the devastating impact of the war on Palestinian civilians.
Entire neighbourhoods have been razed and survivors are left with dwindling supplies of food, water and fuel.
The health ministry in Gaza said hospitals were at breaking point, with more than 30,000 people taking shelter at the Al-Shifa hospital in Gaza City alone.
It said it was "extremely concerned" about disease outbreaks due to poor water supply and sanitation.
"There are corpses in the streets. Buildings are crashing down on their inhabitants," said Jamil Abdullah, a Palestinian-Swede, hoping to flee the blockaded enclave.
"The smell of the dead is everywhere."
The UN works agency UNRWA says more than one million Palestinians -- almost half of Gaza's population of 2.4 million -- have fled their homes.
An UNRWA flour storage near Gaza City was hit by an Israeli strike, an AFP photographer said. Even as the smoke was still rising from the rubble, desperate residents collected flour from the ground.
"We are dying of hunger," said Abu Hussni al-Hujein, 60.
Israel has ordered residents of north Gaza to leave for the south, hoping to clear the area of civilians in preparation for a ground assault that would involve gruelling urban combat.
Entire families, young children and the elderly have gathered belongings and fled to southern Gaza, bedding down in any available space, indoors and out.
Egypt kept closed Gaza's only border crossing not controlled by Israel, Rafah, meaning there is no escape.
Israel has repeatedly struck the area on the Palestinian side and denied reports of any temporary ceasefire deal to open it.
Rafah's closure has so far prevented the escape of thousands of Palestinian-Americans and others hoping to get out of Gaza, or the entry of relief goods now loaded on truck convoys waiting in Egypt.
For now, Gazans remain trapped, with neighbouring Arab nations also fearful that if Palestinians leave the territory, they could be permanently exiled.