Mr. Wadi said this was the seventh strike on the hospital his family had witnessed since setting up a tent outside the facility. This time, instead of awakening in a daze to the sight of smoke rising from one spot in the camp, the heat of flames was everywhere, he said. He saw bodies “scorched and black, like giant lumps of coal.”

The Wadi family is one of scores of families that have set up camp in the parking lot of the compound, hoping that international laws prohibiting attacks on hospitals made the area a safe place to shelter. Instead, these families say, they have survived repeated strikes on the hospital. The latest attack, shortly after 1 a.m. on Monday, triggered a fire that set the camp ablaze.

The Israeli military said in a statement posted to social media that it had been targeting a Hamas command center located near the hospital. The fire that erupted afterward was likely caused by secondary explosions, it said.

Survivors interviewed amid the smoldering remains of the camp told The New York Times that the fast-moving fire had been fueled by the explosions of families’ cooking gas canisters and flames that fed off their plastic tents.

“The most difficult scene you can experience is seeing your neighbors burning alive and not being able to do anything to rescue them,” said Abed Musleh, a 25-year-old who fled northern Gaza and was sheltering in a tent in the parking lot with his wife, two children, and his four sisters. He estimated the fire burned at least 30 tents. Residents scrambled to find any buckets not burned in the blaze to try and help rescuers put out the fire.

The Palestinian health authority said four people died and over a dozen were injured, but that the death toll would likely rise. Later Monday, Doctors Without Borders, which has medics operating in Gaza, said five people were killed and dozens were wounded, some with severe burn injuries.

Despite the repeated strikes, Mr. Musleh had no plans to leave. He cannot find anywhere else to go, he said, and he still couldn’t imagine that any other place would be safer than a hospital.

Israel has come under repeated criticism for hitting civilian infrastructure, including hospitals, during the yearlong war in Gaza. A U.N. report last week accused Israel of a deliberate policy to destroy the health care system. The Israeli military has said it acted on information that Hamas was operating from the hospital compound, and it has repeatedly said that it tries to avoid civilian casualties.

But for Gaza’s two million people, an increasingly common refrain is that nowhere is safe — and that, with more than 90 percent of the population displaced, there are few places left to go.

Mohammed Ramadan, whose family of 10 survived but lost their tent, said he felt trapped by impossible options: “There are no safe places, and no places left to shelter in.”

The shells hit a distribution center in Jabaliya, killing at least 10 people and wounding 40 others, said Juliette Touma, the director of communications for the U.N. Palestinian aid agency, UNRWA. Reuters reported the same death toll, citing Palestinian medics. It was not possible to confirm the reports independently.

Israeli forces have mounted an offensive in north Gaza, an area shattered by a year of Israeli airstrikes and fighting, to prevent Hamas from regrouping. They have directed civilians to leave but more than 400,000 remain, some saying that they have been fatigued by repeated evacuation orders — and that they are doubtful they would be safer elsewhere.

The U.N. human rights office said that Israeli forces appeared to be sealing off north Gaza from the rest of the enclave by erecting sand barriers at a key crossing point and that they had reportedly “opened fire, killing some Palestinians trying to evacuate” farther south. In a statement, it said it was appalled by the bombing in northern Gaza.

The human rights office also said that the separation going up in the area raises concern that Israel does not intend to allow civilians to return to their homes.

Israel’s military did not immediately respond to a request for comment.

The head of UNRWA, Philippe Lazzarini, said that northern Gaza’s health system had all but collapsed and that telecommunications had been cut. The U.N., he said, has not been able to provide any assistance since the end of last month. Basic services have been interrupted or forced to a halt, among them UNRWA’s health center, and only two wells are operational, he said.

The medical aid charity Doctors Without Borders said on Monday that one of its staff members had died after being hit by shrapnel last week in Jabaliya.

The Israeli military agency that oversees policy for the Palestinian territories, COGAT, said that 30 trucks passed a crossing point into northern Gaza on Monday. “Israel is not preventing the entry of humanitarian aid, with an emphasis on food, into Gaza,” it said in a statement.

“It’s a political message of the United States to Israel that, ‘We are with you,’” said Yehoshua Kalisky, a military technology expert at the Institute for National Security Studies in Tel Aviv. “And to enemies, it’s: ‘Don’t.’”

Here is a look at the THAAD system and what it can do.

What is THAAD?

The Terminal High Altitude Area Defense system is a mobile surface-to-air interceptor designed to shoot down incoming ballistic missiles. It is categorized as a short-, medium- and intermediate-range interceptor that can strike incoming targets both within the Earth’s atmosphere and above it.

The system is made up of five parts: Interceptor missiles, launchers, radar, a command-and-control platform, and other support equipment unique to the THAAD. There is no warhead on the missile, which destroys its targets by the force of its impact.

There are only nine active THAAD batteries in the world, according to its manufacturer, Lockheed Martin. Seven of them are assigned to the U.S. Army, and among other locations are deployed in Guam and South Korea. The battery that the Biden administration has ordered to Israel presumably would be among those seven.

Two others are being fielded in the United Arab Emirates.

The Pentagon announced almost a year ago that it was sending a THAAD battery to the Middle East to help protect Israel, but did not specify where it would be.

How will it be used?

Because it can reach above the atmosphere, the THAAD should be able to intercept ballistic missiles launched from Iran and Yemen, said Fabian Hinz, a missiles and Middle East expert at the International Institute for Strategic Studies in London. It can also shoot down shorter-range missiles launched by Hezbollah, in neighboring Lebanon.

Iran and its allies have also fired guided cruise missiles and drones, which operate at much lower altitudes and speeds than ballistic missiles.

Mr. Kalisky said the THAAD would be particularly useful in intercepting debris from other missiles that have been downed before it falls to the ground, where it can inflict casualties and damage infrastructure. (He also said the THAAD has an exceptional radar that can detect incoming missiles from farther distances.)

But Mr. Hinz said they would likely serve as another layer of urgently needed air defenses, given that some Iranian missiles evaded Israeli interceptors during a barrage earlier this month. Iran lies more than 500 miles from Israel.

“We have seen that the Iranian strategy is to fire large volleys in order to overwhelm Israeli defenses,” Mr. Hinz said. “If you have additional interception capability, that is quite useful.”

How is it different from Israel’s other air defense systems?

It’s largely a matter of range, meaning how far the missile can fly. The THAAD has a range of about 125 miles. Its launchers and command centers can be moved to different sites.

Mr. Kalisky compared the THAAD to one of Israel’s main defense systems, the David’s Sling, a stationary weapon at a fixed location that can shoot down short- and medium-range ballistic and cruise missiles. It has a range of about 185 miles and is also a “hit-to-kill” weapon that downs its targets by flying into it. The David’s Sling is jointly produced by Raytheon and Israeli weapons producer Rafael.

Then there is Israel’s Arrow series, which is produced by Israel Aerospace Industries and Boeing.

The Arrow 2 can intercept targets high in the atmosphere, with an altitude of about 30 miles and a range of about 60 miles. It has a fragmentation warhead packed with explosives that can blow up near incoming missiles even if it does not directly hit its targets.

The Arrow 3, another hit-to-kill weapon, can go beyond the atmosphere with a range of up to 1,500 miles. It is one of Israel’s most advanced defenses and was used to counter the Iranian strikes on Oct. 1. Both the Arrow 2 and the Arrow 3 are ground-based mobile launchers.

The Iron Dome system is perhaps the best known of Israel’s air defenses, largely because it is used more than the others. Its short-range interceptors — just 6 inches wide and 10 feet long — rely on miniature sensors and computerized guidance to zero in on short-range rockets. It is produced by Rafael, the Israeli defense contractor.

The Israeli military said in a statement posted to social media that it had been targeting what it described as a Hamas command center located near the hospital. “Shortly after the strike, a fire ignited in the hospital’s parking lot, most likely due to secondary explosions,” the military said. The claims could not be independently confirmed.

The strikes ignited the neat rows of tents, and video taken afterward shows firefighters and volunteers rushing to put out the blazes with hoses and buckets of water. Other footage shows emergency medical workers combing through the smoldering debris in search of casualties.

“The situation is just horrific,” said Louise Wateridge, the Gaza spokesperson for UNRWA, the U.N. agency tasked with aiding Palestinian refugees. She woke up around 3 a.m. to a call from a colleague who had been sheltering in the courtyard with the other families when the airstrike hit. He escaped his tent just in time. Not everyone was so lucky.

“There were no warnings,” Ms. Wateridge said. “Everyone was sleeping.”

Scores of families have been sheltering in the hospital parking lot for the past several months, having fled fighting elsewhere in Gaza. For some, it’s the third or fourth time they have moved in search of shelter. Al Aqsa, as central Gaza’s only functioning hospital, was thought to be relatively safe.

Before the start of the war in Gaza last October, Al Aqsa provided care to tens of thousands of patients every month. Since the fighting began, thousands of Gazans have sought safety inside the compound’s walls, even as it has been struck several times by Israeli forces.

The Israeli military has said that it was acting on information that Hamas was operating from the hospital compound, and it has repeatedly said that it tries to avoid civilian casualties. But its operations have drawn widespread criticism, including from the United Nations, which accused Israel in a report last week of a “concerted policy” to “destroy Gaza’s health care system as part of a broader assault” on Hamas.

Ms. Wateridge of UNRWA asked her colleague where he would go next now that his tent and all his remaining possessions were gone.

“He was completely silent for a moment,” she said. “Then he told me, ‘There is no safe place.’ He thought the hospital was the safest place to be.”

Raja Abdulrahim, Abu Bakr Bashir and Gabby Sobelman contributed reporting.

In July, the Houthi militia in Yemen hit an apartment building in Tel Aviv, killing one civilian. Hezbollah last week hit a nursing home north of Tel Aviv, causing damage but no casualties. Earlier in the year, Hezbollah broadcast footage that was captured by a drone that flew over sensitive installations in Haifa, seemingly without being detected.

The latest strike, on a training base south of the Israeli city of Haifa, highlighted how Hezbollah retains the ability to hurt Israel despite devastating Israeli attacks on its leadership and infrastructure. It also pointed up Israel’s defensive shortcomings, prompting the Israeli military to launch an investigation and its chief spokesman to acknowledge on Sunday: “We must provide better defense.”

One of the civilians who spotted the drone, Viki Kadosh, said she was “so frustrated, because 10 minutes before the hit, we had called in to warn about it.” Speaking on Monday to Galei Tzahal, a radio station run by the Israeli military, Ms. Kadosh said: “We spotted it flying very low, right above our home. We heard the sound it was making and immediately noticed there was something strange about it.” The Israeli military declined to comment.

The sequence of drone attacks has caused alarm in Israel as it prepares for a potential escalation with Iran. After Iran fired a barrage of ballistic missiles at Israel nearly two weeks ago, Israel is widely expected to retaliate, a response that could prompt Iran to fire more missiles and drones.

While Israel has a world-leading system to detect and intercept missiles, which can travel faster than 1,000 miles an hour, its radar systems have found it more challenging to spot unmanned aircraft, which sometimes move slower than 100 miles an hour.

Drones often contain less metal and emit less heat than high-velocity rockets and shells, meaning that they do not always set off alerts. And even when they are spotted, enemy drones are sometimes mistaken for Israeli aircraft, including small private planes, because they fly at similarly low altitudes and speeds.

“All the systems that we have in the Western world — it’s not only Israel — are built to defend or to protect the airspace from regular fighter planes and missiles,” said Ofer Haruvi, a former head of the drone department in the Israeli Air Force. “You need to redesign part of these systems so that they can see and detect and track this kind of slow-moving target.”

Israel’s Iron Dome anti-rocket system destroys the vast majority of rockets fired from Gaza and Lebanon, while its Arrow 3 interceptors were instrumental in largely blocking two massive barrages of ballistic missiles fired by Iran in April and again this month. To enhance those defenses, the United States said on Sunday that it would send Israel another anti-missile system, the Terminal High Altitude Area Defense system, or THAAD.

But Israel’s anti-drone system in particular requires improvement, experts said.

It relies mainly on radar, which is primarily designed to detect relatively large metallic objects like planes by transmitting a signal and receiving the signal’s reflected echo, according to Onn Fenig, the head of R2 Wireless, a company that designs drone detection systems and works with the Israeli military.

He said there are alternatives, including receptors that passively detect and classify the radio waves emitted by a drone, optical sensors that scan the skies for visual signs of a drone and acoustic sensors that detect the sound of a drone’s engine.

All these systems have advantages and blind spots, and Israel needs to combine them in order to build a more robust drone detection system, Mr. Fenig said.

“There’s no magic solution that, if implemented, would solve all your problems,” he said. “But we need a complete change in mind-set.”

Myra Noveck contributed reporting.

The reports had not been independently verified. The facility was to have been used for the second stage of a campaign to vaccinate children in Gaza against polio, Mr. Lazzarini said, but the drive did not take place there because of “severe damage.”

The attack, and one on a hospital nearby, was “another night of horror” and the situation in Gaza was “a never ending hell,” Mr. Lazzarini said on social media on Monday.

Palestinian health authorities say that more than 40,000 people have been killed in the enclave during Israel’s campaign against Hamas, which began after the militant group launched an attack on Israel on Oct. 7 last year in which around 1,200 people were killed.

Israel’s military did not claim responsibility for an attack on the school, but said the incident was under review.

In recent months, Israel’s forces have conducted dozens of airstrikes on schools that in the past year have been turned into shelters for people displaced by the war. In almost every case, it has said that the compounds were being used by Hamas, though it has not provided evidence in support of the claims.

Hundreds of people have been killed in the attacks, which have been criticized as a violation of international law by the United Nations and some governments.

The vaccination campaign restarted on Monday, a month after nearly 560,000 children under the age of 10 were given the first dose of the vaccination against the disease. Aid agencies plan to administer second doses across Gaza over the next two weeks. Israel and Hamas have agreed to pause fighting for several hours a day in areas where vaccines are being administered.

This time, UNRWA said in a statement that it aimed to reach 590,000 children under the age of 10 in less than two weeks, providing vitamin A in addition to the polio vaccine to support the health of children “living in extremely dire hygiene and sanitation conditions.”

The campaign will be run in coordination with Israel’s military to ensure that “the population will be able to safely reach the medical centers where the vaccinations will be given,” according to a statement by COGAT, the Israeli military agency that oversees policy for the Palestinian territories and liaises with international relief organizations.

More than 1,500 Israelis have been killed in the conflict, mostly during Hamas’s attack on Oct. 7. More than 40,000 Palestinians have been killed in Israel’s counterattack, including thousands of children.

An UNRWA spokeswoman, Louise Wateridge, said that, while the campaign was critical, “the children will inevitably return straight back into the dangerous and inhumane conditions they came from.”

The COGAT statement did not mention UNRWA. The agency, which has had more than 200 of its Palestinian employees killed during the war, has been key to efforts to provide shelter, food and other basic services during the war, but Israel accuses it of aiding Hamas. Israel’s parliament has taken steps toward passing a bill branding UNRWA as a terrorist organization.

“The inviolability of U.N. premises must be respected at all times,” Mr. Guterres said in a statement on social media on Sunday. “Attacks against peacekeepers are in breach of international law and may constitute a war crime.”

The Israeli military said that its soldiers had entered the peacekeeping base as they tried to flee from Hezbollah missile fire and were in contact throughout the episode with the U.N. peacekeeping mission, known as UNIFIL.

The mission came under Israeli fire several times last week, and Israeli officials have called on the United Nations to pull its peacekeeping forces back. Prime Minister Benjamin Netanyahu said on Sunday that the United Nations’ refusal to do so “makes them hostages of Hezbollah,” the armed Lebanese group that the Israeli military has been targeting in a weekslong air and ground offensive.

“This endangers both them and the lives of our soldiers,” Mr. Netanyahu said, in a message directed at Mr. Guterres.

The U.N. force has rejected Israel’s calls to leave its positions in southern Lebanon. Mr. Guterres does not have authority over UNIFIL, whose presence is mandated by the U.N. Security Council.

United Nations peacekeeping forces have been in southern Lebanon since 1978. The mission includes over 10,000 civilian and military personnel from 50 countries who are assigned to prevent border violations between Lebanon and Israel over a 75-mile stretch referred to as the Blue Line.

In an overnight call with Israeli Minister of Defense Yoav Gallant, U.S. Defense Secretary Lloyd J. Austin III “reinforced the importance of Israel taking all necessary measures to ensure the safety and security of UNIFIL forces and Lebanese Armed Forces,” the Pentagon press secretary, Maj. Gen. Pat Ryder, said in a statement.

The episode on Sunday was the latest in a series of Israeli challenges to the peacekeeping force since invading southern Lebanon in late September.

On Saturday, UNIFIL reported that Israeli soldiers had blocked peacekeepers’ passage through an area northeast of Ramyah, prompting the mission to issue its fourth warning in recent days to Israel and other parties “to steer clear of the mission’s premises and operations.”

“UNIFIL’s mandate provides for its freedom of movement in its area of operations,” it said.