RAFAH, Gaza Strip — Palestinians who fled an ongoing Israeli raid of Gaza’s main hospital, in the north of the area, described mass arrests and forced marches past bodies in interviews Sunday, while the United Nations said Israel is now blocking its main agency helping Palestinians from sending food aid to the enclave’s devastated north.

Israel’s military says it has killed more than 170 militants and detained about 480 suspects in the raid on Shifa Hospital that began Monday, calling it a blow to Hamas and other armed groups it says had regrouped there as the war nears the six-month mark.

The fighting highlights the resilience of Palestinian armed groups in a heavily destroyed part of Gaza where Israeli troops have been forced to return after a similar raid in the war’s earliest weeks.

Kareem Ayman Hathat, who lived in a five-story building about 100 yards from the hospital, said he huddled in the kitchen for days while some explosions caused the building to shake.

Early Saturday, Israeli troops stormed the building and forced dozens of residents to leave. He said men were forced to strip to their underwear and four were detained. The rest were blindfolded and ordered to follow a tank south as blasts thundered around them.

Israeli jets on Sunday launched several strikes near Shifa Hospital, which largely stopped functioning following the November raid. After saying Hamas had an elaborate command center there, Israeli forces months ago exposed a single tunnel leading to a few underground rooms.

Hardly any aid has been delivered in recent weeks to northern Gaza and Gaza City, where Shifa is located. The isolated area suffered widespread devastation in the early days of Israel’s offensive launched after the Oct. 7 Hamas attack that triggered the war.

As of Sunday, Israel has told the U.N. agency for Palestinian refugees it will no longer approve agency food convoys to northern Gaza, UNRWA chief Philippe Lazzarini said on social media.

“This is outrageous and makes it intentional to obstruct lifesaving assistance during a man-made famine,” he said.

The agency, Gaza’s biggest humanitarian provider, is repeatedly accused by Israel of having links to Hamas. Israel’s government didn’t immediately respond.

Experts have said famine is imminent in northern Gaza, where more than 210,000 people suffer from catastrophic hunger.

A day after standing near some of the estimated 7,000 aid trucks waiting to enter Gaza and calling the starvation a “moral outrage,” U.N. Secretary-General António Guterres urged an immediate humanitarian cease-fire, the release of hostages held in Gaza and Israel’s removal of “obstacles” to allow a flood of aid delivery.

“Looking at Gaza, it almost appears that the four horsemen of war, famine, conquest and death are galloping across it,” Guterres said in Egypt, adding that nothing justifies the collective punishment of Palestinians.

Gaza’s Health Ministry said five wounded Palestinians trapped at Shifa Hospital died without food, water or medical services. The World Health Organization’s director-general, Tedros Adhanom Ghebreyesus, described conditions as “utterly inhumane.”

Jameel al-Ayoubi, among thousands sheltering at Shifa when the current raid began, said tanks and armored bulldozers plowed into the hospital courtyard, crushing ambulances and civilian vehicles. He saw tanks drive over at least four bodies of people killed in the raid.

Israel’s military said Saturday it had evacuated patients and medical staff from Shifa’s emergency department because militants “entrenched” themselves there, and set up an alternative site for seriously wounded patients.

Israel’s military early Sunday also stormed al-Amal and Nasser hospitals in the southern city of Khan Younis amid “very intense shelling,” the Palestinian Red Crescent Society said.

Israel’s military announced operations in Khan Younis targeting Hamas infrastructure but said troops weren’t currently operating in the hospitals.

The war has killed at least 32,226 Palestinians, according to Gaza’s Health Ministry.

Israeli Defense Minister Yoav Gallant said that he was traveling to the U.S. on Sunday at Washington’s invitation, with a goal of preserving “our ability to obtain air systems and munitions” for the war and maintaining critical ties with Israel’s top ally.

In Israel on Sunday, Jews celebrated their most joyful of holidays, Purim, the biblical story of how a plot to exterminate Jews in Persia was thwarted as an affirmation of Jewish survival.