An Israeli air strike has killed at least 20 people including children at a school in Gaza, according to two local hospitals.

The school in Nuseirat was sheltering some of the many Palestinians displaced by the war.

Meanwhile, explosions hit early on Monday outside Al-Aqsa Martyrs Hospital in Deir al-Balah, killing three people and injuring about 50 others, the hospital said. Tents caught fire, and residents of the Central Gaza community carried the injured into the hospital.

Israel is continuing to strike what it says are militant targets in Gaza almost daily.

The military says it tries to avoid harming civilians and blames their deaths on Hamas and other armed groups because they operate in densely populated areas.

In northern Gaza, Israeli air and ground forces have been attacking Jabaliya, where the military says militants have regrouped.

Over the past year, Israeli forces have repeatedly returned to the built-up refugee camp, which dates to the 1948 war surrounding Israel’s creation, and other areas.

Israel has ordered the full evacuation of northern Gaza, including Gaza City.

An estimated 400,000 people remain in the north after a mass evacuation ordered in the war’s opening weeks.

Palestinians fear Israel intends to permanently depopulate the north to establish military bases or Jewish settlements there.

The United Nations says no food has entered northern Gaza since October 1.

The military confirmed that hospitals were included in evacuation orders but said it had not set a timetable and was working with local authorities to facilitate patient transfers.

Fares Abu Hamza, an official with the Gaza Health Ministry’s emergency service, said the bodies of a “large number of martyrs” remain uncollected from the streets and under rubble.

“We are unable to reach them,” he said, adding that dogs are eating some remains.

The war began when Hamas-led militants attacked a year ago, killing 1,200 people, mostly civilians, and abducting around 250.

Around 100 hostages are still held in Gaza but a third are believed to be dead.

Israel’s bombardment and its ground invasion of Gaza have killed more than 42,000 Palestinians, according to Gaza’s Health Ministry, and left much of the territory in ruins.

Israel says it has killed more than 17,000 fighters.