Israeli forces battled Hamas-led fighters in several parts of the Gaza Strip on Tuesday, and the Palestinian health officials said at least 57 people were killed in Israeli bombardments of southern and central areas.

In Rafah, a southern border city where Israeli forces have been operating since May, five Palestinians were killed in an airstrike on a house, Gaza health officials said. In nearby Khan Younis, a man, his wife, and two children were killed, they said.

An Israeli air strike on a UN-run school that housed displaced families in the Nuseirat refugee camp killed 23 people and wounded many others, health officials said.

The Israeli military said in a statement it had attacked a group of "terrorists" who had operated from inside the school, after taking steps to mitigate the risk to civilians.

On Tuesday, the United Nations Relief and Works Agency for Palestine Refugees (UNRWA) said on social media platform X that five UNRWA schools have been hit in the last 10 days.

"UN facilities must be protected at all times. They must never be used for military or fighting purposes," the refugee agency said.

"No one is safe in Gaza, wherever they are. The people of Gaza are children, women and men, who have the right to live," it added.

On the same day, the UN Office for the Coordination of Humanitarian Affairs (OCHA) said one of the multiple strikes across Gaza occurred just a few hundred meters from the UN Joint Humanitarian Operations Center.

OCHA said UN agencies and non-governmental organizations use the base located in Deir al Balah to coordinate work throughout the Gaza Strip.

On the displacement side, humanitarians report families continue to move from Gaza City to Deir al Balah, with more than 1,000 people observed crossing in just the past week.

The humanitarians said the lack of electricity and fuel continues to impact essential service providers, including hospitals, ambulances, bakeries and aid trucks. Over the past two weeks, the UN has collected an average of about 80,000 liters of fuel per day, up from about 45,000 liters per day in the last two weeks of June.

"While this represents an improvement, the requirement for the most basic humanitarian operations stands at 400,000 liters per day, and the Israeli authorities are still not allowing the allocation of fuel to key local humanitarian responders, preventing them from transferring supplies within Gaza," OCHA said.

Hamas has accused Israel of stepping up attacks in Gaza to try to derail efforts by Arab mediators and the United States to reach a ceasefire deal. Israel says it is trying to root out Hamas fighters.

Efforts to end the conflict stalled on Saturday after three days of negotiations failed to produce a viable outcome, Egyptian security sources said.

A Palestinian official close to the negotiations told Reuters Hamas was keen not to be seen as halting the talks despite the stepped-up Israeli attacks.

"Hamas wants the war to end, not at any price. It says it has shown the flexibility needed and is pushing the mediators to get Israel to reciprocate," the official said.

U.S. State Department spokesperson Matthew Miller said on Monday that two senior advisers to Netanyahu had said Israel was still committed to reaching a ceasefire.

(With input from agencies)