Hospitals in Gaza faced collapse Monday as water, power and medicine neared depletion, while hundreds of thousands of Palestinians faced dwindling food supplies as Israel maintained punishing airstrikes in retaliation for last week's deadly rampage by Hamas. Thousands of patients’ lives were at risk, U.N. officials said, and mediators struggled for a cease-fire to let in aid waiting at the Egyptian border.

More than a week after Israel stopped entry of essential supplies, all eyes were on the Rafah crossing between Gaza and Egypt. Trucks carrying badly needed aid have waited there for days unable to pass through. Israeli airstrikes last week forced the shutdown of Rafah, Gaza’s only connection to Egypt.

Egypt’s Foreign Minister Sameh Shoukry said Israel “has not taken a position” on allowing access. The Israeli government did not respond to a request for comment.

As Israel prepared a likely ground offensive into Gaza that would mean deadly house-to-house fighting, fears rose over the conflict spreading. Israel evacuated towns near its northern border with Lebanon. Hamas militants in Gaza continue to fire rockets into Israel.

Speaking to the Israeli Knesset on Monday, Prime Minister Benjamin Netanyahu warned Iran and Hezbollah, “Don’t test us in the north. Don’t make the mistake of the past. Today, the price you will pay will be far heavier,” referring to Israel’s 2006 war with Hezbollah, which operates out of Lebanon.

This has become the deadliest of the five Gaza wars for both sides. At least 2,778 have been killed and 9,700 wounded in Gaza, according to the Heath Ministry there. More than 1,400 Israelis have been killed, the vast majority civilians in Hamas’ Oct. 7 assault. The Israeli military said Monday that at least 199 hostages were taken back in Gaza, higher than previous estimates. The military did not specify whether that number includes foreigners.

The combination of airstrikes that pulverize entire neighborhoods, depleting supplies, and Israel’s mass evacuation order for the north of the Gaza Strip threw the tiny territory’s 2.3 million people into upheaval. More than 1 million have fled their homes, and 60% of them are now in the approximately 14-kilometer-long (8 mile) area south of the evacuation zone, according to the U.N.

The Israeli military says it is trying to clear away civilians for their safety ahead of a major campaign against Hamas in Gaza's north, where it says the militants have extensive networks of tunnels and rocket launchers. Much of Hamas’ military infrastructure is in residential areas.

Those fleeing northern Gaza still faced the threat of airstrikes in the south. Before dawn Monday, a strike hit a building in the town of Rafah where three displaced families who fled Gaza City were sheltering. At least 12 people were killed and nine others remained missing, said survivors from the al-Masry, al-Akhras and Hamouda families. The strike reduced the house to a vast crater blanketed with wreckage.

More than 400,000 displaced people in the south were crowded in schools and other facilities of the U.N. agency for Palestinians, UNRWA. But the agency can't provide them aid, leaving them to search for water and food. UNRWA said it has only 1 liter of water a day for each of its staff members trapped in the territory.

Hundreds of thousands more displaced have moved in with family members, packing dozens into homes.

With taps dry, many have resorted to drinking dirty or sewage-filled water, risking the spread of disease.

“Gaza is running out of water, and Gaza is running out of life,” said UNRWA chief Philippe Lazzarini, calling for a lifting of the siege. “We need this now.”

The few operating bakeries had long snaking lines of people. Ahmad Salah in the city of Deir al-Balah said he waited 10 hours to get a kilo (2 pounds) of bread to feed 20-30 family members.

For a third day, Israel’s military announced a safe corridor for people to move from north to south between the hours of 8 a.m. and noon. It said more than 600,000 people have already evacuated the Gaza City area.

In northern Gaza, unknown numbers remained, either unwilling or unable to leave.

UNRWA said 170,000 people were sheltering at its schools in the north when the order to leave came. But it couldn't evacuate them and doesn’t know if they remained. More than 40,000 have crowded in the grounds of Gaza City’s al-Shifa Hospital and surrounding streets, hoping it will be safe from bombardment.

UNRWA said Monday it received reports that the Hamas-run Ministry of Health removed fuel and medical equipment from its evacuated compound in Gaza City.

Hamas urged people to ignore the evacuation order. The Israeli military on Sunday released photos it said showed a Hamas roadblock preventing traffic from moving south.

Hospitals in Gaza are expected to run out of generator fuel in the next 24 hours, the U.N. said.

Four hospitals in northern Gaza are no longer functioning and 21 have received Israeli orders to evacuate. Doctors have refused, saying it would mean death for critically ill patients and newborns on ventilators.

The medical aid group Doctors With Borders said many of its personnel decided to stay in the north to treat wounded. They had run out of painkillers, and staff reported “wounded screaming in pain," it said.

Israel has said the siege won’t be lifted until Hamas releases all the captives, but the country’s water ministry said water had been restored at one “specific point” in Gaza, outside the southern town of Khan Younis. Aid workers in Gaza said they had not yet seen evidence the water was back.

The World Health Organization said assistance for 300,000 patients was currently awaiting entry through Rafah. On the Gaza side of the crossing, crowds of Palestinians with dual citizenship waited anxiously, sitting on suitcases or crouched on the floor, some comforting crying infants.

“They are supposed to be a developed country, talking about human rights all the time,” Shurouq Alkhazendar, whose two kids are American citizens, said of the United States. “You should protect your citizens first, not leave them all alone suffering and being humiliated in front of the crossing.”

After increasing cross-border exchanges with Hezbollah in the north, the Israeli military ordered residents to evacuate 28 communities within 2 kilometers (1.2 miles) of the Lebanese border.

“Israel is ready to operate on two fronts, and even more,” said Rear Adm. Daniel Hagari, a military spokesman.

Hezbollah released video showing snipers shooting out cameras on several Israeli army posts along the border, apparently to prevent Israel from monitoring movements on the Lebanese side.

The U.S. government began evacuating some 2,500 American citizens by ship from the Israeli port city of Haifa to Cyprus. Commercial airlines have largely stopped flying into Israel’s Ben-Gurion International Airport.

U.S. Secretary of State Antony Blinken returned to Israel for a second time in less than a week after a six-country tour through Arab nations aimed at preventing the fighting from igniting a broader conflict. President Joe Biden is also considering a trip to Israel, though no plans have been finalized.

Biden postponed a planned trip to Colorado on Monday to talk about his domestic agenda and instead will hold meetings with top aides on the Israel-Hamas conflict.

In a television interview Sunday night, Biden, who has repeatedly proclaimed support for Israel, said he thought it would be a “big mistake” for the country to reoccupy Gaza.

Israel’s ambassador to the U.N., Gilad Erdan, told CNN the country does not want to occupy Gaza but will do “whatever is needed” to obliterate Hamas’ capabilities.

Israeli forces, supported by a growing deployment of U.S. warships in the region and the call-up of some 360,000 reservists, have positioned themselves along Gaza’s border and drilled for what Israel said would be a broad campaign to dismantle Hamas. Israel said it has already struck dozens of military targets, including command centers and rocket launchers, and also killed Hamas commanders.