Airstrikes on a Gaza hospital compound on Tuesday killed at least 500 people, the health ministry said.
"300 to 500 displaced people killed in Israeli strikes on the yard" of the Ahli Arab hospital in central Gaza, the ministry said.
"Hundreds of victims are still under the rubble," it added.
The media office described the attack as a "war crime".
"The hospital was housing hundreds of sick and wounded, and people forcibly displaced from their homes" because of other strikes, a statement said.
An Israeli military spokesman would not immediately confirm its forces bombed the hospital.
"We will look into it ... the strike happened just a short while ago, " Daniel Hagari said in a televised press briefing.
Around 3,000 people have been killed in Israeli air strikes across the Gaza Strip since the war erupted on October 7.
More than 1,400 people in Israel have been killed, the majority gunned down by Hamas who crossed from Gaza and attacked border communities.
The Israeli military blamed on a failed rocket launch by a Palestinian militant group.
The Israeli army said the strike which hit the hospital was a rocket misfired by the Palestinian fraction.
Analysis indicated "that a barrage of rockets was fired by Hamas in Gaza, passing in close proximity to Ahli hospital in Gaza at the time it was hit," the military said in a statement issued more than two hours after the deadly explosion.
The strike on the Al-Ahli Al-Arabi hospital in the north of the Gaza Strip that killed hundreds was "unprecedented in scale," the World Health Organization (WHO) said on Tuesday, condemning the attack.
The strike was the bloodiest single incident in Gaza since Israel launched a bombing campaign against the densely populated Gaza Strip in retaliation for a deadly cross-border Hamas assault on Israeli communities on Oct. 7.
"This attack is unprecedented in scale," said Richard Peeperkorn, WHO Representative for the West Bank and Gaza. "We have seen consistent attacks on healthcare in the occupied Palestinian territory."
Peeperkorn said there so far have been 51 attacks against healthcare facilities in Gaza, with 15 health workers killed and 27 injured.