In the Jabaliya refugee camp on Gaza City’s outskirts, at least six airstrikes destroyed a number of apartment blocks in a residential area, the Hamas-run Interior Ministry said. It reported a large number of casualties but did not immediately provide details.

Footage of the scene from Al-Jazeera TV showed at least four large craters where buildings once stood, amid a large swath of rubble surrounded by partially collapsed structures. Dozens of rescue workers and bystanders dug through the wreckage, searching for survivors beneath the pancaked buildings. A group of young men pulled two children from the upper floors of a damaged apartment block, cradling them as they climbed down.

More than half the territory’s 2.3 million Palestinians have fled their homes, with hundreds of thousands sheltering in packed U.N.-run schools-turned-shelters or in hospitals alongside thousands of wounded patients. Israeli strikes have hit closer to several northern hospitals in recent days, alarming medics.

Thousands of people broke into its aid warehouses over the weekend to take food, as supplies of basic goods have dwindled because of the Israeli siege.

There has been no central electricity in Gaza for weeks, and Israel has barred the entry of fuel needed to power emergency generators for hospitals and homes.

UNRWA, which hundreds of thousands of people in Gaza rely on for basic services even in normal times, says 64 of its staff have been killed since the start of the war, including a man killed alongside his wife and eight children in a strike late Monday.

“This is the highest number ever of U.N. aid workers killed in any conflict around the world in such a short time,” spokesperson Juliette Touma told The Associated Press. “UNRWA will never be the same without these colleagues.”

The war has also threatened to ignite fighting on other fronts. Israel and Lebanon’s Hezbollah militant group have traded fire daily along the border, and Israel and the U.S. have struck targets in Syria linked to Iran, which supports Hamas, Hezbollah and other armed groups in the region.

The military said it shot down what appeared to be a drone near the southernmost city of Eilat and intercepted a missile over the Red Sea on Tuesday, neither of which entered Israeli airspace.

The Iran-backed Houthi rebels in Yemen later issued a video statement claiming to have fired ballistic missiles and drones at Israel, saying it was the third such operation. They threatened to carry out more strikes “until the Israeli aggression stops.”

Earlier this month, a U.S. Navy destroyer in the Red Sea intercepted three cruise missiles and several drones launched toward Israel by the Houthis, who control much of northern Yemen, including its capital, Sanaa. Projectiles have also struck inside Egypt, near the Israeli border.

In the occupied West Bank, where Israeli-Palestinian violence has also surged, the army demolished the family home of Saleh al-Arouri, a senior Hamas official exiled over a decade ago. Ali Kaseeb, head of the local council in the village of Aroura, said the home had been vacant for 15 years.

More than 8,500 Palestinians have been killed in the war, mostly women and minors, the Gaza Health Ministry said Monday, without providing a breakdown between civilians and fighters. The figure is without precedent in decades of Israeli-Palestinian violence.

Over 1,400 people have died on the Israeli side, mainly civilians killed during Hamas’ initial attack, also an unprecedented figure. Palestinian militants have continued firing rockets into Israel.

Larger ground operations have been launched north and east of Gaza City. Jonathan Conricus, an Israeli military spokesman, called Gaza City the “center of gravity of Hamas” but said strikes continue in other parts of the territory.

The military said it struck some 300 militant targets over the past day, including compounds inside tunnels, and that troops had engaged in several battles with militants armed with antitank missiles and machine guns. Video footage released by the military showed soldiers and a tank moving down a dirt road between two rows of demolished buildings, some of them three to four stories high.

Hamas released its own video showing what it said was a battle in northern Gaza on Sunday. A fighter wearing a GoPro-style camera emerged from a tunnel with a rocket-propelled grenade launcher and ran across sand dunes and shrubs with other militants amid the clatter of gunfire.

It was not possible to independently confirm reports by either side.

Casualties are expected to mount on both sides as the battle moves into dense, residential neighborhoods.

Conricus said some 800,000 people have heeded the Israeli military’s orders to flee from the northern part of the strip to the south. Northern Gaza was estimated to have a pre-war population of around 1.1 million.

The window to flee south may be closing, as Israeli forces reached Gaza’s main north-south highway this week. Video circulating Monday showed a tank opening fire on a car that had approached a sand berm but was turning around. Gaza’s Health Ministry said three people were killed.

Zaki Abdel-Hay, a Palestinian living a few minutes’ walk from the road south of Gaza City, said people are afraid to use it. “People are very scared. The Israeli tanks are still close,” he said over the phone, adding that “constant artillery fire” could be heard near the road.

Dawood Shehab, a spokesperson for Islamic Jihad, a smaller militant group allied with Hamas, told Al Jazeera television that its fighters were battling Israeli forces who were trying to cut off the main highway and a parallel coastal road farther west.

In a news conference late Monday, Netanyahu rejected calls for a cease-fire to facilitate the release of captives or end the war, which he has said will be long and difficult. “Calls for a cease-fire are calls for Israel to surrender to Hamas,” he told a news conference. “That will not happen.”

The military said Monday that special forces rescued one of the estimated 240 captives seized by Palestinian militants during the wide-ranging assault. It said Pvt. Ori Megidish, 19, was “doing well” and had been reunited with her family.

Hamas has released four hostages, and has said it would let the others go in return for thousands of Palestinian prisoners held by Israel, which has dismissed the offer.

Gaza’s humanitarian crisis, meanwhile, continues to worsen.

The World Health Organization said two hospitals have been damaged and an ambulance destroyed in Gaza over the last two days. It said all 13 hospitals operating in the north have received Israeli evacuation orders in recent days. Medics have refused such orders, saying it would be a death sentence for patients on life support.

Israel says it targets Hamas fighters and infrastructure and that the militants operate among civilians, putting them in danger.

Israel has allowed more than 150 trucks loaded with food and medicine to enter Gaza from Egypt over the past several days, but aid workers say it’s not enough to meet rapidly growing needs.