(BSS/AFP) - An Israeli military order for residents and displaced people in Gaza`s Deir el-Balah area to move south dealt "another devastating blow" to humanitarian efforts in the war-ravaged territory, the UN`s OCHA aid agency said on Sunday.

The United Nations Office for the Coordination of Humanitarian Affairs "warns that today`s mass displacement order issued by the Israeli military has dealt yet another devastating blow to the already fragile lifelines keeping people alive across the Gaza Strip," it said in a statement.

On Sunday morning, the Israeli military ordered those in the central Gaza area to leave immediately due to imminent operations, with whole families seen lugging their few belongings and heading south.

OCHA said UN staff were "remaining" in the territory and their coordinates had been shared with "relevant parties."

"These locations -- as with all civilian sites -- must be protected, regardless of displacement orders," OCHA said, warning that any damage to health clinics, water infrastructure, and aid warehouses in the area "will have life-threatening consequences."

Between 50,000 and 80,000 people were in the area when the evacuation order was issued, according to OCHA`s initial estimates.

Since the start of the war, nearly all of Gaza`s population -- which is also facing severe food shortages -- has been displaced at least once by repeated Israeli evacuation orders.

According to OCHA, the latest order means that 87.8 percent of Gaza`s area is now under displacement orders or within Israeli militarized zones.

That leaves "2.1 million civilians squeezed into a fragmented 12 per cent of the Strip, where essential services have collapsed," said the UN agency.

The order "will limit the ability of the UN and our partners to move safely and effectively within Gaza, choking humanitarian access when it is needed most."

Israel on Sunday withdrew the residency permit of the head of the OCHA office in the country, Jonathan Whittall, who has repeatedly condemned the humanitarian conditions in Gaza.

Israel`s military campaign in Gaza has killed 58,895 Palestinians, mostly civilians, according to the health ministry in the Hamas-run territory. The UN finds these figures credible.

The war was sparked by Hamas`s 2023 attack on Israel in which 1,219 people, most of them civilians, were killed, according to an AFP tally based on official figures.