UNITED NATIONS - The last remaining civilian lifelines are collapsing in Gaza City as Israel's military onslaught triggers more casualties, mass displacement, destruction, and tighter restrictions on humanitarian work, UN humanitarians said on Thursday.

The UN Office for the Coordination of Humanitarian Affairs (OCHA) said that in just the past five days, 11 emergency shelters for about 11,000 people in Gaza City have taken direct or indirect hits. The shelters were located on the premises of the UN Relief and Works Agency for Palestine Refugees in the Near East.

OCHA said that its partners tracking the movement of people reported that the number of displacements within the Gaza Strip is rising fast, now exceeding 1 million since the ceasefire collapsed in mid-March. As of Wednesday, 200,000 displacements were recorded from northern to southern Gaza over the past month, including 56,000 since Sunday.

"OCHA is alarmed by increasing reports of displaced families sleeping on the streets or in makeshift tents and struggling to survive," the office said. "Despite heavy restrictions, the United Nations and its partners are doing everything possible to reach people across Gaza with life-saving support."

OCHA said its efforts to provide relief are not without challenge. Zikim, the only crossing directly into the north, where famine has been confirmed, has been shut since the weekend.

The office said that Israeli authorities have also classified some food items, such as peanut butter, as "luxuries" not to be allowed in, leaving large amounts of already-procured aid stuck outside Gaza. Inspection rules vary by route, creating unpredictability and needless delays.

Within Gaza, OCHA said some humanitarian movements were also blocked.

Just Wednesday, three of 14 coordinated movements were denied, including two intended to bring food to the north. Two other missions faced obstacles that meant they could only be partially completed or were prevented from being carried out.

The office said the obstacles wasted time and human resources, missed opportunities to reach people in need, and exposed aid workers to unnecessary risks.

"The aid reaching people falls far short of what they need, and the cost is measured in lives," the office said. "OCHA warns that opportunities to support starving people are being systematically blocked. Every week, new restrictions are imposed."

OCHA released a summary on Thursday of what relief the world body and its partners were able to deliver in the first half of the month.

The office said that to tackle famine and food insecurity, humanitarian teams collected over 12,500 tonnes of wheat flour, food parcels and bulk supplies from the Israeli-controlled crossings. They served nearly 560,000 meals daily through 116 kitchens and provided 10,000 loaves of bread to those moving to the south.

OCHA said to address cases of malnutrition, the United Nations and its partners continued to screen children and enroll them for treatment.

The UN Children's Fund reported dispatching over 200,000 packs of nutrient-rich baby food to partners, enough to support over 63,000 infants and young children for two weeks. They also dispatched 10,000 boxes of high-energy biscuits, enough to assist more than 10,000 acutely malnourished pregnant and breastfeeding women for one month.

"We need a ceasefire, we need hundreds of trucks every day, safe and open routes. We need an end to bureaucratic delays. We need restoration of power and water, and more meaningful commercial imports," Stephane Dujarric, chief spokesman for UN Secretary-General Antonio Guterres, said at a regular briefing.

"We need the release of all the hostages that are still being held in Gaza by Hamas and other groups, immediately and unconditionally and we need arbitrarily detained Palestinians freed from Israeli detention centers," he added.