An Israeli strike early Thursday on a school sheltering displaced Palestinians in central Gaza killed more than 30 people, including 23 women and children, according to local health officials in the Hamas-run Palestinian territory. The hospital treating victims said it had received the bodies of at least "37 martyrs" from the strike, according to Agence France-Presse. But a U.N. official tells the Reuters news agency the death toll is between 35 and 45, though it still can't confirm any numbers.

Israel Defense Forces spokesperson Lieutenant Colonel Peter Lerner said the IDF had been monitoring the school and that 20-30 Hamas and affiliated militants were "operating in three different rooms to plan and launch terror attacks."

"We have been following the activity there in the last few days and we postponed the strike twice to allow a precise attack and avoid hurting innocents," Lerner said, adding that he was "not aware of civilian casualties" and urging caution in accepting the figures suggested by officials in Gaza. He said the IDF was still "checking the numbers."

The IDF didn't immediately offer evidence of a combatant presence in the school, but it released a photo pointing to classrooms on the second and third floor where it claimed the militants were located.  

Hamas says cease-fire proposal "does not lay the correct foundations for the required agreement"

The strike came as U.S., Qatari and Egyptian mediators resumed talks seeking a cease-fire and hostage release deal, but a statement shared Thursday morning by Hamas, dated June 5, criticized what the group characterized as differing explanations of the latest proposal by the U.S. and Israel. 

The statement said President Biden, in announcing the draft on May 31 as an Israeli proposal, had confused the situation and accused Israel of issuing subsequent "contradictory statements" regarding its backing of the deal.

"After examining the content of the Israeli paper, it became clear that it is a paper that does not lay the correct foundations for the required agreement, as it does not guarantee a permanent cease-fire, but rather a temporary cease-fire," Hamas said, adding that it still took a "positive stance towards Biden's statements," but claiming they did not align with the terms in the proposal drafted by Israel. 

CBS News has sought clarification from Hamas on the position laid out it its statement, but has not received a reply.

Hamas stressed in its statement that it was "ready to agree to any agreement that includes" three foundations for a truce laid out by Mr. Biden at the end of May.

The White House, along with Israel and many other Western nations, have pressured Hamas publicly to accept the deal announced by the Mr. Biden a week ago.

Israel says it won't end the war without destroying Hamas, and it has rejected calls for a permanent cease-fire until that aim is achieved. The militant group is demanding a lasting cease-fire and the full withdrawal of Israeli forces from Gaza.

Israel's Gaza offensive intensifies 

The bloody scenes at the Gazan school came after the IDF announced a new ground and air assault in several refugee camps in central Gaza, pursuing Hamas militants it says have regrouped there.

It's the latest instance of troops sweeping back into sections of the Gaza Strip they'd previously invaded, underscoring the resilience of the militant group despite Israel's nearly eight-month onslaught in the territory.

Witnesses and hospital officials said the predawn strike hit the al-Sardi School, run by the U.N. agency for Palestinian refugees, known by the acronym UNRWA. The school was filled with Palestinians who had fled Israeli offensives and bombardment in northern Gaza, they said.

Ayman Rashed, a man displaced from Gaza City who was sheltering at the school, said the missiles hit classrooms on the second and third floor where families were sheltering. He said he helped carry out five dead, including an old man and two children, one with his head shattered open. "It was dark, with no electricity, and we struggled to get out the victims," Rashed said.

The Al-Aqsa Martyrs Hospital in the nearby town of Deir al-Balah received at least 33 dead from the strike, including 14 children and nine women, according to hospital records and an Associated Press reporter at the hospital. Another strike on a house overnight killed six people, according to the records. Both strikes occurred in Nuseirat, one of several built-up refugee camps in Gaza dating to the 1948 war surrounding Israel's creation, when hundreds of thousands of Palestinians fled or were driven from their homes in what became the new state.

Mohammed al-Kareem, a displaced Palestinian sheltering near the hospital, described chaotic scenes outside the facility. He said vehicles arrived one after the other as distressed people rushed wounded people into the emergency department. Videos circulating online appeared to show several wounded people being treated on the floor of the hospital, a common scene in Gaza's overwhelmed medical wards.

Footage showed bodies wrapped in blankets or plastic bags being laid out in lines in the courtyard of the hospital, which was largely dark as staff try to conserve limited fuel for electricity. Al-Kareem said he saw people searching for their loved ones among bodies and that one woman kept asking medical workers to open the wraps on the bodies to see if her son was inside.

"The situation is tragic," he said.

UNRWA schools across Gaza have functioned as shelters since the start of the war, which has driven most of the territory's 2.3 million Palestinians from their homes.

Israel launched its campaign in Gaza after Hamas' Oct. 7 attack in Israel, in which militants killed some 1,200 people and took about 250 others hostage. About 80 of those individuals are still believed to be alive and held captive in Gaza.

Israel's offensive has killed more than 36,000 Palestinians, according to Gaza's Hamas-run Health Ministry, which doesn't distinguish between fighters and civilians in its figures.

Israel blames civilian deaths on Hamas, accusing it of consistently positioning fighters, tunnels and rocket launchers in residential areas and buildings.

Doctors Without Borders said at least 70 bodies and 300 wounded people, mostly women and children, were brought to a hospital in central Gaza on Tuesday and Wednesday after a wave of Israeli strikes.

The international charity said Wednesday in a post on X that Al-Aqsa Martyrs Hospital is struggling to treat "a huge influx of patients, many of them arriving with severe burns, shrapnel wounds, fractures, and other traumatic injuries."

Gaza's health system has nearly collapsed through almost eight months of war. The hospital, which was treating some 700 wounded and sick people before the latest strikes, said Wednesday that one of its two electric generators had stopped working, threatening its ability to keep operating ventilators and incubators for premature babies.

Israel has routinely launched airstrikes in all parts of Gaza since the start of the war and has carried out massive ground operations in the territory's two largest cities, Gaza City and Khan Younis, that left much of them in ruins.

Israel sent troops into the southern city of Rafah in May in what it said was a limited incursion, but those forces are now operating in central parts of the city on Gaza's southern border with Egypt. More than 1 million people have fled Rafah since the start of the operation, with many heading toward central Gaza, where Israel's operations have ramped up in recent days.

CBS News' Haley Ott contributed to this report.

In:
• War
• Hamas
• Israel
• United Nations
• Gaza Strip
• Benjamin Neta​nyahu