Troops rounded up men and ordered women to leave the Jabalia historic refugee camp, they said. An Israeli airstrike on a house in Jabalia killed five people and wounded several others, medics said. 

The UN Palestinian refugee agency UNRWA said Israeli authorities were preventing humanitarian missions from reaching areas in the north of the Palestinian enclave with critical supplies, including medicine and food.

"People attempting to flee are getting killed, their bodies left on the street," UNRWA head Philippe Lazzarini said on X.

Medics at the Indonesian Hospital told Reuters that Israeli troops stormed a school and detained the men before setting it ablaze. The fire reached hospital generators and caused a power outage, they added.

Health officials said they had refused orders by the Israeli army, which started a new incursion into the territory's north over two weeks ago, to evacuate the three hospitals in the area or leave the patients unattended.

Later on Monday, Hussam Abu Safiya, director of Kamal Adwan Hospital said at least two critically wounded patients at the facility's intensive care unit died because of the lack of medical supplies.

"The hospital's blood units have run out completely... We are implementing a priority treatment method for patients. This is the reality," said Abu Safiya in a video message to media outlets.

Troops remained outside the hospital but did not enter, they said. Medics at a second hospital, Kamal Adwan, reported heavy Israeli fire near the hospital at night.

"The army is burning the schools next to the hospital, and no one can enter or leave the hospital," said one nurse at the Indonesian Hospital, who asked not to be named.

Palestinian health officials said at least 18 people had been killed in Jabalia and eight elsewhere in Gaza in Israeli strikes. 

On Saturday, Gaza's health ministry said two patients at the Indonesian hospital died during a siege by Israeli forces around the facility on Saturday, while Israel's military reported its troops were operating in the area.

Since dawn, Israeli forces had surrounded and shelled the Indonesian Hospital in the northern town of Beit Lahia, Gaza health officials said.

t said the military operation caused "the death of two patients inside the Indonesian Hospital in the northern Gaza Strip, as a result of the hospital's siege and the power outage and (lack of) medical supplies".

The ministry did not provide details about the two patients, their illnesses or the exact cause of their deaths.

In an earlier statement, the ministry said Israel had targeted the upper floors of the Indonesian Hospital, adding there were "more than 40 patients and wounded in addition to the medical staff" present.

"Heavy gunfire" towards the hospital and its courtyard had sparked a "state of great panic" among patients and staff, it added.

When asked for a response to the ministry's allegation that the two patients had died due to the military siege, the Israeli army told AFP that its troops were "operating near the Indonesian Hospital".

"The troops operating in the area have been trained for the operational activity and briefed on the importance of mitigating harm to civilians and medical infrastructure," the military said in a statement.

"It is emphasised that the hospital continues to operate without disruption and in full capacity, and there was no intentional fire directed at it."

Last week, the United States told Israel it must take steps in the next month to improve the humanitarian situation in Gaza or face potential restrictions on US military aid.

Israel has intensified its campaigns both in Gaza and Lebanon after the killing of Hamas leader Yahya Sinwar last week had raised hopes of an opening for ceasefire talks to end more than a year of conflict.

It has vowed to eradicate Hamas, the group who formerly controlled Gaza and whose attack on Israel last year triggered the war, but in doing so has laid waste to much of the territory and killed tens of thousands of people. More than 1.9 million people have been left destitute and desperate for food.

"We are facing death by bombs, by thirst and hunger," said Raed, a resident of Jabalia camp. "Jabalia is being wiped out and there is no witness to the crime, the world is blinding its eyes." 

Hadeel Obeid, a supervisor nurse at the Indonesian hospital, said they were running out of medical supplies, including sterile gauze and medications. The water supply has been cut off and there was no food for the fourth consecutive day, she told Reuters.

The United Nations said it had been unable to reach the three hospitals in northernGaza.

The UN Human Rights Office accused Israeli forces of unlawful interference with humanitarian assistance and issuing orders that were causing forced displacement. It said their conduct "may be causing the destruction of the Palestinian population in Gaza's northernmost governate through death and displacement".

UNRWA'S Lazzarini said injured people were lying without care in hospitals that had been hit.

"UNRWA remaining shelters are so overcrowded, some displaced people are now forced to live in the toilets," he said.

Israel's subsequent bombardment of Gaza has killed more than 42,500 Palestinians, with another 10,000 uncounted dead thought to lie under the rubble, Gaza health authorities say.