UNITED NATIONS, July 2 (Xinhua) -- The latest Israeli displacement order isolates a key Gaza reservoir, prompting UN humanitarians on Wednesday to warn that any damage could collapse the Khan Younis water system.

The UN Office for the Coordination of Humanitarian Affairs (OCHA) said the new displacement order for two neighborhoods in Khan Younis, following reported Palestinian rocket fire, covers almost 80,000 people.

"Our colleagues working on water, sanitation and hygiene also tell us that Al Satar, a key water reservoir, has become inaccessible as a result of the order," OCHA said. "The facility serves as the main water distribution hub for Khan Younis and a critical supply point for water coming through the Israeli pipeline in the area. Any damage to the reservoir could lead to a collapse of the city's water distribution system, with grave humanitarian consequences."

OCHA said the displacement orders continue to strain vital services and push people into increasingly smaller swaths of Gaza's territory. Since the breakdown of the ceasefire in March, as of Tuesday, 714,000 people had been forcibly displaced once more across the strip, with nearly 29,000 displaced in just the 24 hours between Sunday and Monday.

The office said that approximately 85 percent of Gaza's territory is either under displacement orders or located within militarized zones, severely hampering people's access to essential humanitarian support and the ability of aid workers to reach those in need.

"Many existing shelters are severely overcrowded, with poor hygiene conditions, posing severe risks for public health," OCHA said. "Our partners working on health, water, sanitation and hygiene report that across Gaza, rates of acute watery diarrhea have reached 39 percent among patients receiving health consultations."

The humanitarians said the increase is being driven by insufficient clean drinking and domestic water reaching shelters, worsening the dire hygiene and sanitation conditions. The governorates of Gaza and Khan Younis have the worst levels of acute watery diarrhea due to severe overcrowding in sites and shelters.

The office said that no shelter assistance has entered Gaza in four months, despite the hundreds of thousands of newly displaced people.

"Our shelter partners say that 97 percent of the sites surveyed reported displaced people sleeping in the open," OCHA said. "An unrestricted flow of supplies through multiple crossing points over a sustained period of time is critical to address people's needs and prevent the already desperate situation from worsening."

The office said the depletion of fuel stocks continues to wreak havoc on aid operations, constraining the United Nations and humanitarian partners' ability to respond.

An attempt to deliver some of the remaining fuel stocks to the north was denied on Wednesday by Israeli authorities. The denial follows a successful delivery on Tuesday of diesel from the World Health Organization's remaining stock to Al Shifa Hospital in Gaza City to prevent further shutdown of critical services, said OCHA.

Partners working on emergency telecommunications reported that, unless fuel stocks are replenished immediately, Gaza could face a complete communications blackout, severely hindering humanitarian access and coordination and preventing affected communities from receiving life-saving information, said the office.

"Critical water, sanitation, hygiene and health care facilities have already begun shutting down in some areas, including hospital equipment and services, water trucking and water and sewage pumps," the humanitarians said. "If the fuel crisis isn't addressed soon, humanitarian responders could be left without the systems and tools necessary to operate safely, manage logistics and distribute humanitarian assistance."

This would endanger aid workers and escalate an already dire humanitarian crisis, warned OCHA. Enditem