Israel has warned the UN that 1.1 million Palestinians should evacuate the northern Gaza Strip within the next 24 hours, according to a report.

The Israeli Ministry of Defense and its army suggested UN staff and Gazans flee to the southern portion of the strip, an indication of a stronger, more intense attack to come against Hamas by the Jewish nation.

“Today, just before midnight local time, team leaders of the UN Office of the Coordination of Humanitarian Affairs and the Department of Safety and Security in Gaza were informed by their liaison officers in the Israeli military that the entire population of Gaza north of Wadi Gaza should relocate to southern Gaza within the next 24 hours,” UN spokesperson Stéphane Dujarric told Axios.

The notification was issued to ensure that the roughly 1.1 million people who live in the area would be spared by Israel’s planned military actions and operations.

But the evacuation is “impossible,” Dujarric said, adding that it would cause “devastating humanitarian consequences.”

“The United Nations strongly appeals for any such order, if confirmed, to be rescinded avoiding what could transform what is already a tragedy into a calamitous situation,” she said.

The short-notice evacuation warning comes just hours after Israel declared a “complete siege” on the enclave, including halting supplies of electricity, food, water and fuel.

Israel’s Energy Minister Israel Katz said on Thursday that supplies would remain cut off until the estimated 150 hostages being held by Hamas in Gaza are freed.

“No electrical switch will be turned on, no water hydrant will be opened, and no fuel truck will enter until the Israeli abductees are returned home. Humanitarian for humanitarian. And no one will preach us morals,” Katz said.

The blockade is posing a major risk for the strip’s overwhelmed hospital systems, which are on the brink of a “humanitarian catastrophe,” the World Health Organization warned.

Israel has unrelentingly attacked and bombed the enclave since Hamas launched a surprise attack on the country and its unsuspecting civilians Saturday.

More than 1,500 Palestinians have been killed by Israeli airstrikes in retaliation to Hamas’ deadly weekend attack, according to the Ministry of Health in Gaza.

Another 338,000 Gaza residents have been displaced by the conflict, according to the UN.

At least 12 UN employees have been killed in the chaos.