DEIR AL-BALAH, Gaza Strip: An Israeli airstrike hit a school-turned-shelter in Gaza early Saturday, killing at least 80 people, Palestinian health authorities said, in one of the deadliest strikes in the 10-month-old war between Israel and Hamas.

The Israeli military acknowledged it targeted the Tabeen school in central Gaza City, claiming it hit a Hamas command center within the school. Hamas denied that.

The United Nations said the latest strike was part of Israel’s increasing attacks on Gaza’s schools, which have been turned into shelters for people who have been forced to flee their homes by the war.

Video from the scene showed walls blown out on the ground level of a large building. Concrete chunks and twisted metal lay atop the blood-soaked floor, along with clothing, toppled furniture and other debris. A blackened car with the windows blown out was covered in rubble.

Fadel Naeem, director of the Al-Ahli hospital in Gaza City, told The Associated Press that the facility received 70 bodies of those killed in the strike and the body parts of at least 10 others. The Health Ministry said another 47 people were wounded.

Naeem said some of the wounded had severe burns and many had to have limbs amputated.

“We received some of the most serious injuries we encountered during the war,” he said.

The strike hit without warning in the early morning before sunrise as people were praying at a mosque inside the school, according to Abu Anas, a witness who worked to rescue people.

“There were people praying, there were people washing and there were people upstairs sleeping, including children, women and old people,” he said. “The missile fell on them without warning. The first missile, and the second. We recovered them as body parts.”

Three missiles ripped through the two-story building — the first floor housing the mosque and the second the school — where about 6,000 displaced people were taking shelter from the war, said Mahmoud Bassal, a spokesperson for the Civil Defense first responders who operate under the Hamas-run local government.

Many of the dead were unrecognizable, and many of the casualties were women and children, he said.

The UN had previously said that as of July 6, 477 out of 564 schools in Gaza had been directly hit or damaged in the war. In a report Saturday, the UN Human Rights Office said there have been at least 21 attacks on schools since July 4, leaving hundreds dead including women and children. Many of the schools were serving as shelters, the report said, adding that Israel has a duty under international law to provide safe shelter for the displaced.

“There’s no justification for these massacres,” EU foreign policy chief Josep Borrell said in a statement posted on the social media platform X, in reference to the strikes on schools.

Israel has blamed civilian deaths in Gaza on Hamas, saying the group endangers noncombatants by using schools and residential neighborhoods as bases for operations and attacks.

Israeli intelligence indicated about 20 militants from Hamas and Islamic Jihad, including senior commanders, were using the Tabeen school compound to plan attacks on Israeli forces, Lt. Col. Nadav Shoshani, an Israeli military spokesman said in a statement on X. Shoshani also questioned the casualty numbers issued by the Palestinian Health Ministry.

Izzat Al-Rishq, a top Hamas official denied there were militants in the school.

Israel said the targeted school was located next to a mosque serving as a shelter for Gaza City residents.

A cameraman working for The Associated Press said, however, that the mosque and the classrooms were in one building, with the prayer hall on the ground floor and the school above it. A missile appeared to have penetrated through the floor of the classrooms to the mosque below and then exploded, according to the cameraman.

The strike came as American, Qatari and Egyptian mediators renewed their push for the two parties to achieve a ceasefire agreement that could help calm soaring tensions in the region following the assassination of top Hamas political leader Ismail Haniyeh in Tehran and a senior Hezbollah commander in Beirut.

Egypt, which borders Gaza and serves as a key mediator, said the strike on the school showed Israel had no intention of reaching a ceasefire deal and ending the war. Neighboring Jordan condemned the attack as a “blatant violation” of international law. Qatar demanded an international investigation, calling it a “heinous crime” against civilians.

Late Friday, two separate airstrikes in central Gaza killed at least 13 people including three children and seven women, hospital authorities said. An Associated Press journalist counted the bodies at the Al-Aqsa Martyrs hospital in the central city of Deir Al-Balah.

One strike hit a house in the Nuseirat refugee camp, killing seven people, all but one of them women, hospital officials said. Another hit a house in Deir Al-Balah, killing six, including a woman and her three children, the hospital said.

Israel’s campaign in Gaza has killed more than 39,790 Palestinians and wounded more than 92,000 others, according to the Health Ministry, in the Hamas-run territory, which does not distinguish between combatants and civilians in its tally. The war was triggered by Hamas’ Oct. 7 attack, in which militants from Gaza stormed into southern Israel, killing around 1,200 people and abducting 250 others.

More than 1.9 million of Gaza’s prewar population of 2.3 million have been driven from their homes, fleeing repeatedly across the territory to escape offensives. Most are now crowded into ramshackle tent camps in an area of about 50 square kilometers (19 square miles) on the Gaza coast.