An Israeli airstrike hit a school-turned-shelter in Gaza City early Saturday, killing more than 60 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 the strike, claiming it hit a Hamas command centre within the school.

The strike on the Tabeen school in central Gaza City also wounded dozens more people, the Health Ministry’s Ambulance and Emergency Service said. The facility, like almost all of Gaza’s schools, has been used as a shelter for people who have been forced to flee their homes by the war.

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 school and the mosque inside, 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 government.

Many of the dead were unrecognizable, he said, adding that he expected the death toll to rise. Many of the casualties were women and children, he said.

According to the United Nations, 477 out of 564 schools in Gaza have been directly hit or damaged in the war as of July 6. In June, an Israeli strike on a school sheltering displaced Palestinians in central Gaza killed at least 33 people, including 12 women and children, according to local health officials.

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

In its statement Saturday, the Israeli military said the school was located next to a mosque serving as a shelter for Gaza City residents.