JERUSALEM — Israel’s intensifying military assault on northern Gaza has pushed areas of the enclave to the edge of humanitarian collapse, according to U.N. and aid officials, with the area’s last functioning hospital close to failing, emergency responders unable to move freely and food supplies dipping toward dangerous levels after a near-total blockade on aid deliveries to North Gaza since the beginning of the month.

“People suffering under the ongoing Israeli siege in North Gaza are rapidly exhausting all available means for their survival,” U.N. Secretary General António Guterres tweeted Wednesday.

Conditions have deteriorated in the weeks since the Israel Defense Forces launched a renewed offensive in parts of northern Gaza, an area where more than 400,000 civilians are estimated to be living amid destroyed buildings and shattered infrastructure. Basic functions in the worst-hit areas are collapsing, residents and aid workers said.

Gaza’s Civil Defense agency, which conducts search and rescue operations, said it was pulling out of North Gaza because of threats from Israeli forces, spokesman Mahmoud Bassal said in a statement.

“Several team members have been targeted and injured, and others are lying on the streets, bleeding, with no one able to rescue them,” he said on Telegram early Thursday.

Some medical supplies are now in such short supply that doctors are forced to choose which of the injured to treat, according to Mohammad Wadi, the deputy project coordinator for Doctors Without Borders in Gaza.

“My colleagues tell me that now they have to decide which patient can we help, which ones we leave to die,” Wadi said by phone from Gaza City. “It’s really horrible to see a patient who can breathe and still watch him die, but this is beginning to happen in the north.”

Israel, which says it has ramped up military operations to keep Hamas from regrouping in the area, has struck sites across the north. At least 73 people were killed last week when missiles hit a group of homes in the town of Beit Lahia, Gazan officials said.

In some areas, victims have remained under rubble for days as emergency crews were prevented from reaching them, the U.N. humanitarian aid office, OCHA, said earlier this week. As many as 40 people were believed to be trapped in a destroyed building in the Fallujah neighborhood, near the Jabalya refugee camp, the agency said.

For five days after that strike, the United Nations asked Israeli forces to permit them to escort civil defense workers to dig casualties out from under the rubble. Israeli authorities denied the requests each time, most recently Wednesday. Now, humanitarian workers presume those people are dead, Georgios Petropoulos, the head of OCHA’s Gaza operation, said Thursday.

Citing intense bombardments and a lack of assured humanitarian pauses across the north, the World Health Organization on Wednesday suspended the third phase of its polio vaccination program, which aimed to inoculate more than 119,000 children in northern Gaza against a reappearance of the polio virus — a campaign that had been touted as a rare example of successful international-Israeli cooperation in the enclave.

“The conditions of North Gaza governorate are beyond catastrophic,” Petropoulos told The Washington Post on Tuesday after a visit to the area.

Israeli officials say they have worked to warn civilians away as the offensive has ramped up, issuing evacuation orders and directing residents to head as far south as possible. More than 60,000 people have been displaced from northern Gaza to Gaza City, OCHA said Tuesday.

But many civilians report that routes farther south were blocked by Israeli troops and active combat, leaving them effectively trapped. Advocates said thousands, including the elderly and children, were unable to travel at all in the war-ravaged north. And many who have been displaced multiple times in the past year would rather take their chances by staying put than head to already overcrowded tent camps in the south.

Critics say Israel’s actions in the north suggested it has begun to implement a plan endorsed by far-right government ministers to gain control of parts of Gaza by forcing civilians out and shooting or starving those who are left through a military siege. The IDF and senior government officials have denied the accusations.

U.S. Secretary of State Antony Blinken raised concerns about the alleged plan to Prime Minister Benjamin Netanyahu during an in-person meeting this week, according to U.S. officials who spoke on the condition of anonymity to discuss the sensitive talks. Netanyahu responded that such a proposal “was absolutely not our policy,” they said.

The prime minister’s office declined to comment.

Blinken — who is on a multi-stop tour of the Middle East aimed at cooling tensions between Israel, Hamas in Gaza and Hezbollah in Lebanon — on Thursday announced plans to send an additional $135 million in humanitarian aid for Gaza and the West Bank.

Speaking to reporters in Qatar, he also said that U.S. and Israeli negotiators will travel to Doha in the coming days to attempt to reach a cease-fire and hostage deal in Gaza. The upcoming meeting represents the latest effort by the United States to forge a cease-fire after the killing of Hamas leader Yahya Sinwar.

Israel, meanwhile, has blamed the United Nations and humanitarian groups for the slow pace of aid delivery to northern Gaza — even though the Israeli military controls the entry of all goods into Gaza and determines the routes by which aid can be delivered inside the enclave.

Israel cut off aid entirely during at least two weeks earlier this month, which the Israeli government attributed to security conditions in the area. Israel said aid has resumed since a northern crossing was reopened last week.

“At this time there is no obstacle to the introduction of humanitarian aid into the northern Gaza Strip,” the government said in a court filing Wednesday in response to a lawsuit brought by several Israeli human rights organizations petitioning for more aid to the enclave.

But aid groups said the little food entering the north is not reaching the hardest-hit areas, and that Israel has not approved most requests from aid organizations to bring food and other critical humanitarian supplies from the south to the north.

And getting any aid into the Strip at all has been significantly complicated by the lack of security and looting of aid trucks seeking to ferry aid from the Kerem Shalom crossing in the south — the main crossing point for aid since Israel seized and closed the Rafah crossing with Egypt in May.

“It’s a little charade we play day in and day out about trying to navigate the nuances of a crossing that’s engineered to fail,” Petropoulos said.

Gaza officials said that rescue and paramedic teams would pull out of north Gaza after the IDF targeted crews Wednesday, wounding at least three members and forcing another to leave an area where they were working.

The IDF did not immediately respond to a request for comment.

One of the rescue workers, Mohammed Tamous, said his team was working in the Beit Lahia area when Israeli quadcopter drones surrounded them and, via loudspeakers, ordered them to abandon their vehicles and rescue gear and head to a nearby hospital.

“When we left, they attacked us by firing a group of shells,” Tamous said in a voice recording sent to journalists Thursday. “A large number of us were injured, and others scattered in the streets, not knowing where to go.”

Some residents asked the paramedics to leave the area, Tamous said, out of fear that the crews were being targeted.

“We are not terrorists, we provide humanitarian services,” he said.

Parker reported from Jerusalem, Hudson from Doha and Harb from London.

previous coverage

• Israel and UN are maneuvering fraught, but fundamental ties during Middle East wars
• Blinken urges Israel to seek enduring deal, as officials say a limited cease-fire has been discussed