Jabalia has been the focus of an Israeli offensive for around 10 days and the military has now encircled the camp and sent tanks into nearby Beit Lahiya and Beit Hanoun towns.
As the operation has continued, people there have been caught between Israeli demands to move south and Hamas calls not to leave because it was too risky to do so.
On Monday, 10 people were killed and 40 wounded by tank shelling in Jabalia, including women and children, Palestinian medics said, while another eight were killed in a separate incident in Gaza City’s Sheikh Radwan district.
The United Nations human rights office said the Israeli military appeared to be “cutting off North Gaza completely from the rest of the Gaza Strip”.
“The separation of North Gaza raises further concerns that Israel does not intend to allow civilians to return to their homes, and the repeated calls for all Palestinians to leave northern Gaza raise grave concerns of large-scale forced transfer of the civilian population,” it said in a statement.
Israeli officials said evacuation orders were aimed at separating Hamas fighters from civilians.
The United Nations has described dire conditions affecting the civilian population remaining in Jabalia, with more than 50,000 people displaced and water wells, bakeries, medical points and shelters shut down.
UN Secretary General Antonio Guterres condemned the level of civilian casualties in northern Gaza.
The northern part of Gaza, home to well over half the territory’s 2.3mn people, was heavily bombed in the first phase of Israel’s assault on the territory and hundreds of thousands of residents quit their homes following Israeli evacuation orders.
Around 400,000 people remained, according to United Nations estimates.
Fears that Israel intends to empty northern areas have been fuelled by a proposal floated by former Israeli generals, which calls for north Gaza to be cleared of civilians and remaining militants to be put under siege until they surrender.