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.
Palestinian health officials said at least 18 people had been killed in Jabalia and eight elsewhere in Gaza in Israeli strikes.
Israel’s bombing and ground offensives in Gaza have killed 42,603 people, a majority civilians, according to data from the health ministry in the Hamas-run territory, figures the UN considers reliable.
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.
Medics at the Indonesian Hospital said 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.
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.
More than 1.9mn people have been left destitute and desperate for food.
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 northern Gaza.