What we know about the deadly blast on the Al Ahli Arab Hospital in Gaza

In the wake of a devastating blast at the Al Ahli Arab Hospital in Gaza that killed hundreds of people and injured many others, chaos, finger-pointing and massive demonstrations around the world intensified Wednesday.

Israeli authorities blame the hospital blast on a misfired rocket launched by militants in Gaza, while Palestinian officials claim it was an Israeli airstrike.

Here is what is known and what remains unclear about the explosion:

Explosion rocks center of Gaza City

As darkness fell on the Gaza Strip Tuesday evening, a massive explosion and fireball erupted at the Al Ahli Arab Hospital, also referred to as the Baptist Hospital, in the center of Gaza City. Hundreds of Palestinians injured in Israeli airstrikes in retaliation for the Oct. 7 sneak attack by the Hamas militant group on Israel were being sheltered there.

The blast appeared to have occurred in the hospital's parking area. Video emerging in the chaotic moments following the blast showed cars on fire in the parking lot, ambulances rushing to the scene and medics pulling injured people, including many women and children, out of harm's way. The screams of victims could be heard in the footage.

"We were operating in the hospital, there was a strong explosion, and the ceiling fell on the operating room. This is a massacre," said Dr. Ghassan Abu Sittah, a physician in Gaza for the humanitarian group Doctors Without Borders, who was at the hospital during the blast.

Dr. Hussam Abu Safiya, the lead physician in Gaza for the humanitarian health organization MedGlobal, said the number of patients from the blast arriving at hospitals and clinics in Gaza left medical professionals "overwhelmed."

"We are struggling to help the victims of today's bombing in addition to the patients already crowding in our facility," Abu Safiya said in a statement. "We can't deal with the large number of deaths and injuries. Most victims today were women and children sleeping in the hospital. We now expect more hospitals to be bombed. There is no safe place in Gaza."

Chaotic aftermath

The Gaza Health Ministry said 471 people were killed and 314 others were injured, including 28 who remain in critical condition.

Shortly after the blast, the Gaza Health Ministry released a statement blaming Israeli forces for the incident, saying a "bombing" killed hundreds of civilians forced to flee from the north of the Gaza Strip and left scores of others injured. Hezbollah, the Shiite Muslim political party and militant group based in Lebanon, also held Israeli forces responsible for the blast, saying it "exposes the American and Western support for this criminal occupation."

Palestinian Authority President Mahmoud Abbas and Jordanian government officials canceled a planned summit with President Joe Biden on Wednesday because of the Gaza hospital incident. Abbas blamed Israel for shelling the hospital.

"This is a crime that will never be forgotten and not forgiven," Abbas said Tuesday night. "I decided to cancel the summit with President Biden today. I called on all Palestinians for unity and do not go after divisions; nobody will use division but the enemy of the Palestinian people. Seventy-five years of suffering, displacement, colonialism and all violations of international law."

But Mark Regev, a senior adviser to Israeli Prime Minister Benjamin Netanyahu, said in an interview with Fox News that Israel is investigating the explosion, saying, "We would not have deliberately targeted a hospital" and "it is possible that a Hamas rocket malfunctioned."

In a news briefing, Daniel Hagari, a spokesperson for the Israel Defense Forces, claimed, citing IDF intelligence information, that the hospital was hit when an "enemy rocket barrage was carried out towards Israel, which passed in the vicinity of the hospital."

Late Tuesday night, Netanyahu delivered a statement, saying, "The barbaric terrorists in Gaza are the ones who attacked the hospital in Gaza, not the IDF."

Israeli President Isaac Herzog blamed the Palestinian Islamic Jihad for the hospital disaster, alleging a missile fired by the group "killed many Palestinians at a Gazan hospital -- a place where lives should be saved."

"Shame on the media who swallow the lies of Hamas and Islamic Jihad -- broadcasting a 21st century blood libel around the globe. Shame on the vile terrorists in Gaza who willfully spill the blood of the innocent," Herzog said.

After arriving in Israel Wednesday morning, Biden said during a joint appearance with Netanyahu that Israel was not responsible for the hospital explosion, citing U.S. defense intelligence data.

"I'm deeply saddened and outraged by the explosion at the hospital in Gaza yesterday and based on what I've seen, it appears as though it was done by the other team, not you," Biden told Netanyahu. "But there's a lot of people out there who are not sure. So, we've got to overcome a lot of things."

Biden was asked by a reporter what made him confident that the Israelis weren't behind the explosion. The president responded that it was "the data I was shown by my Defense Department."

Two U.S. officials told ABC News the Pentagon independently concluded the Gaza hospital blast was likely caused by an errant Palestinian Islamic Jihad rocket that fell short of its target.

Protests, condemnation break out

The World Health Organization immediately condemned what it described as an "attack on the Al Ahli Arab Hospital, saying the facility was "operational, with patients, health and caregivers, and internally displaced people sheltering there." It said the hospital was one of 20 in the northern Gaza Strip facing an evacuation order from the Israeli military "that has been impossible to carry out given the current insecurity, critical condition of many patients and lack of ambulances, staff, health system bed capacity and alternative shelter for those displaced."

The WHO called for the immediate active protection of civilians and health care.

"Evacuation orders must be reversed. International humanitarian law must be abided by, which means health care must be actively protected and never targeted," the WHO said in a statement.

United Nations Secretary-General António Guterres "strongly condemned" the hospital blast, saying his heart is with the families of those who died and warning that medical personnel are protected under international law. He made two humanitarian appeals, one for Hamas militants to release the roughly 200 hostages it took in the surprise attack on Israel and secondly to Israel to allow the people of Gaza unrestricted access to humanitarian aid.

"I call for an immediate humanitarian cease-fire to provide sufficient time and space for my two appeals and to ease the epic human suffering that we are witnessing," Guterres said.

Meanwhile, protesters outraged by the horrific Gaza hospital explosion held demonstrations outside U.S. and Israeli embassies around the world, some of which turned violent.

On Tuesday night, Jordanian security forces used tear gas to disperse demonstrators supporting Palestinians in the vicinity of the Israeli Embassy in Amman, Jordan. Pro-Palestinian protesters in Beruit, Lebanon, hurled rocks at the U.S. Embassy, prompting security forces to deploy tear gas and water cannons at them.

In the Iranian capital Tehran, massive crowds of protesters took to the streets early Wednesday in support of the Palestinian people. Dozens were seen setting the Israeli national flag on fire and chanting "death to Israel."

Other large pro-Palestinian protests broke out in Tunis, the West Bank and Yemen.

In Washington, D.C., a large group of protesters from Jewish Voice for Peace staged a demonstration Wednesday afternoon in the Cannon Office Building of the Capitol complex, calling for a cease-fire in the ongoing war between Israel and Hamas. The protesters chanted and carried signs reading "ceasefire" and "let Gaza live." Multiple demonstrators were forcibly removed and some were arrested by U.S. Capitol Police for occupying the rotunda, where television news cameras are usually placed.

The Anti-Defamation League, a leading Jewish group that combats antisemitism and other discrimination, has labeled Jewish Voice for Peace as "radical" and "anti-Israel," with views that fall outside the "mainstream Jewish community."

On its website, the Jewish Voice for Peace describes itself as "the largest progressive Jewish anti-Zionist organization in the world." In a full-page ad the group took out in The New York Times on Wednesday, it further described itself as "American Jews and allies" who are "demanding the Biden administration facilitate an immediate ceasefire, and stop sending the Israeli military more weapons."

"Those of us grieving both Israeli and Palestinian loved ones this week know there is no military solution. The only future is peace and safety for all -- grounded in freedom, justice and equality," the group said in the paid advertisement.