KHAN YOUNIS, Gaza Strip — A massive blast rocked a Gaza City hospital packed with wounded and other Palestinians seeking shelter Tuesday, killing hundreds of people, the Hamas-run Health Ministry said. Hamas blamed an Israeli airstrike, while the Israeli military said the hospital was hit by a rocket misfired by Palestinian militants.

The health ministry said at least 500 people had been killed. Video that The Associated Press confirmed was from the hospital showed fire engulfing the building and the hospital’s grounds strewn with torn bodies, many of them young children. Around them in the grass were blankets, school backpacks, and other belongings.

The carnage came as the U.S. tried to convince Israel to allow the delivery of supplies to desperate civilians, aid groups, and hospitals in the tiny Gaza Strip, which has been under a complete siege since Hamas’ deadly rampage in southern Israel last week.

It also came a day before President Joe Biden was due to visit the region to show support for Israel and try to prevent the war from spreading.

Hundreds of Palestinians had taken refuge in al-Ahli and other hospitals in Gaza City in past days, hoping they would be spared bombardment after Israel ordered all residents of the city and surrounding areas to evacuate to the southern Gaza Strip.

Hamas called Tuesday’s hospital strike “a horrific massacre,” saying it was caused by an Israeli strike.

The Israeli military, however, said Palestinian militants had fired a barrage of rockets near the hospital at the time. “Intelligence from multiple sources we have in our hands indicates that Islamic Jihad is responsible for the failed rocket launch,” it said.

‘I Think Gaza’s Medical Sector Will Collapse Within Hours,’ Says Medical Director

Ambulances and private cars rushed some 350 casualties from the al-Ahli blast to Gaza City’s main hospital, al-Shifa, already overwhelmed with wounded from other strikes, said its director, Mohammed Abu Selmia. The wounded were laid onto bloody floors, screaming in pain.

“We are squeezing five beds into a single tiny room. We need equipment, we need medicine, we need beds, we need anesthesia, we need everything,” Abu Selmia said, warning that the fuel supply for the hospital’s generators will run out Wednesday. “I think Gaza’s medical sector will collapse within hours.”

Before the al-Alhi Hospital deaths, Israeli strikes on Gaza killed at least 2,778 people and wounded 9,700, according to the Gaza Health Ministry. Nearly two-thirds of those killed were children, a ministry official said. Another 1,200 people across Gaza are believed to be buried under the rubble, alive or dead, health authorities said.

Hamas’ Oct. 7, attack in southern Israel killed more than 1,400 people, mostly civilians, and took some 200 captive into Gaza. Hamas militants in Gaza have launched rockets every day since, aiming at cities across Israel.

In protest over the purported airstrike, Palestinian President Mahmoud Abbas canceled his participation in a meeting with Biden, Jordan’s King Abdullah II, and Egypt’s president set for Wednesday in Amman, Jordan to discuss the war. Abbas’ Palestinian Authority runs parts of the West Bank.

In the south, continued strikes killed dozens of civilians and at least one senior Hamas figure Tuesday in attacks it says are targeted at militants. U.S. officials worked to convince Israel to allow delivery of supplies to desperate civilians, aid groups, and hospitals after days of failed hopes for an opening in the siege.

With Israel barring entry of water, fuel, and food into Gaza since Hamas’ brutal attack last week, U.S. Secretary of State Antony Blinken secured an agreement with Israeli Prime Minister Benjamin Netanyahu to discuss creation of a mechanism for delivering aid to the territory’s 2.3 million people. U.S. officials said the gain might appear modest, but stressed that it was a significant step forward.

No Deal to Deliver Aid to 2.3 Million in Gaza

Still, as of late Tuesday, there was no deal in place. A top Israeli official said Tuesday his country was demanding guarantees that Hamas militants would not seize any aid deliveries. Tzahi Hanegbi, head of Israel’s National Security Council, suggested entry of aid also depended on the return of hostages held by Hamas.

“The return of the hostages, which is sacred in our eyes, is a key component in any humanitarian efforts,” he told reporters, without elaborating whether Israel was demanding the release of all of the roughly 200 people Hamas abducted before allowing supplies in.

U.S. President Joe Biden prepared to head to the region as he and other world leaders tried to prevent the war from sparking a broader regional conflict. Violence flared Tuesday along Israel’s border with Lebanon, where Iranian-backed Hezbollah militants operate.

Israeli Troops Gather at the Border

With tens of thousands of troops massed along the border, Israel has been expected to launch a ground invasion into Gaza — but plans remained uncertain.

“We are preparing for the next stages of war,” military spokesman Lt. Col. Richard Hecht said. “We haven’t said what they will be. Everybody’s talking about a ground offensive. It might be something different.”

In Gaza, dozens of injured were rushed to hospitals after heavy attacks outside the southern cities of Rafah and Khan Younis, residents reported. Bassem Naim, a senior Hamas official and former health minister, reported 27 people were killed in Rafah and 30 in Khan Younis.

An Associated Press reporter saw around 50 bodies brought to Nasser Hospital in Khan Younis. Family members came to claim the bodies, wrapped in white bedsheets, some soaked in blood.

An airstrike in Deir al Balah reduced a house to rubble, killing a man and 11 women and children inside and in a neighboring house, some of whom had evacuated from Gaza City. Witnesses said there was no warning before the strike.

Israeli Shelling Hits UN School, Killing Six

Shelling from Israeli tanks hit a U.N. school in central Gaza where 4,000 Palestinians had taken refuge, killing six people and wounding dozens, the United Nations Palestinian refugee agency said. At least 24 U.N. installations have been hit the past week, killing at least 14 of the agency’s staff.

The Israeli military said it was targeting Hamas hideouts, infrastructure, and command centers.

A Top Hamas Commander Killed

A barrage of strikes crashed into the Bureij refugee camp in central Gaza, leveling an entire block of homes and causing dozens of casualties among families inside, residents said. Among those killed was one of Hamas’ top military commanders, Ayman Nofal, the group’s military wing said — the most high-profile militant known to have been killed so far in the war.

Nofal, formerly the intelligence chief of Hamas’ armed wing, was in charge of Hamas militant activities in the central Gaza Strip, including coordinating activities with other militant groups.

Netanyahu sought to put the blame on Hamas for Israel’s retaliatory attacks and the rising civilian casualties in Gaza. “Not only is it targeting and murdering civilians with unprecedented savagery, it’s hiding behind civilians,” he said.

In Gaza City, Israeli airstrikes also hit the house of Hamas’ top political official, Ismail Haniyeh, killing at least 14 people. Haniyeh is based in Doha, Qatar, but his family lives in Gaza City. The Hamas media office did not immediately identify those killed.

Israel sealed off Gaza after the Oct. 7 Hamas attack on southern Israel that killed over 1,400 people, mostly civilians, and resulted in some 200 taken captive into Gaza. Hamas militants in Gaza have launched rockets every day since, aiming at cities across Israel.

Israeli strikes on Gaza have killed at least 2,778 people and wounded 9,700, according to the Gaza Health Ministry. Nearly two-thirds of those killed were children, a ministry official said.

Another 1,200 people across Gaza are believed to be buried under the rubble, alive or dead, health authorities said.

1 Million Palestinians Flee Their Homes

More than 1 million Palestinians have fled their homes — roughly half of Gaza’s population — and 60% are now in the approximately 14-kilometer (8-mile) long area south of the evacuation zone, the U.N. said.

Aid workers warned that the territory was near complete collapse. Hospitals were on the verge of losing electricity, threatening the lives of thousands of patients, and hundreds of thousands of people searched for bread and water.

The U.N. agency for Palestinians said more than 400,000 displaced people are crowded into schools and other facilities in the south. The agency said it has only 1 liter of water a day for each of its staff members trapped in the territory.

Israel Opens Water Line for 3 Hours

Israel opened a water line into the south for three hours that benefitted only 14% of Gaza’s population, the U.N. said.

At the Rafah crossing, Gaza’s only connection to Egypt, truckloads of aid were waiting to enter. The World Food Program said that it had more than 300 tons of food waiting to cross into Gaza.

Civilians with foreign citizenship — many of them Palestinians with dual nationalities — also waited in Rafah, desperate to get out.

“We come to the border crossing hoping that it will open, but so far there is no information,” said Jameel Abdullah, a Swedish citizen.

Repeated reports that an opening was imminent have proven false as negotiations continued to grind on, including the U.S., Israel, and Egypt.

Biden Will Visit Israel on Wednesday

Biden’s visit to Israel on Wednesday will signal the White House’s support for a key ally. He will also travel to Jordan to meet with Arab leaders amid fears the fighting could spread in the region.

Israel evacuated towns near its northern border with Lebanon, where the military has exchanged fire repeatedly with Hezbollah militants.

Israel said it killed four militants wearing explosive vests who were attempting to cross into the country from Lebanon on Tuesday morning. No group immediately claimed responsibility.

Iran’s Supreme Leader Ayatollah Ali Khamenei warned that Israel’s continuing offensive in Gaza could cause a violent reaction across the region.

“Bombardments should be immediately stopped. Muslim nations are angry,” Khamenei said, according to state media.