The head of the United Nations Relief and Works Agency for Palestine Refugees in the Near East (UNRWA) said Gaza has "become the graveyard of children" and "starving people" amid the ongoing war between Israel and Hamas.

On Thursday, the U.N. said at least 798 people have been killed near and around food aid sites, including the U.S.-backed Gaza Humanitarian Foundation (GHF), since the end of May. Among these, 615 people were killed in the vicinity of GHF sites and 183 near aid convoys, the organization said.

"Inaction [and] silence are complicities," Philippe Lazzarini, commissioner-general of UNRWA, wrote in a post on X on Friday. "Under our watch, Gaza has become the graveyard of children [and] starving people. No way out. Their choice is between [two] deaths: starvation or being [shot] at."

In a request for comment from ABC News on Saturday on the 615 people allegedly killed in the vicinity of GHF sites since they opened, the Israel Defense Forces (IDF) said in a statement it "allows the American civilian organization (GHF) to distribute aid to Gaza residents independently, and operates in proximity to the new distribution zones to enable the distribution alongside the continuation of IDF operational activities in the Gaza Strip."

"Following incidents in which harm to civilians who arrived at distribution facilities was reported, thorough examinations were conducted in the Southern Command and instructions were issued to forces in the field following lessons learned," the statement read, in part. "The aforementioned incidents are under review by the competent authorities in the IDF."

The IDF has said it has only shot at people who were posing a threat to others.

The Hamas-run Gaza Ministry of Health reported on Saturday that at least 29 people were shot and killed near a GHF site in Rafah, in southern Gaza.

In a statement to ABC News on the incident Saturday, the IDF said that a review "found no known injured individuals from IDF fire adjacent to the aid distribution site in Rafah" and cautioned against "unverified reports."

The GHF told ABC News that it determined "there was no incident at or near our site."

The U.S. State Department did not immediately return ABC News' request for comment.

Additionally, on Thursday, 15 people -- including nine children and four women -- were killed while waiting in line for nutritional supplies for children in Deir al Balah, in central Gaza. The aid was being distributed by Project Hope, a UNICEF partner organization, according to UNICEF.

In reference to the latter event in Deir al Balah, the IDF told ABC News it was targeting a Hamas militant who participated in the Oct. 7, 2023, terrorist attack in Israel and that "the incident is under review."

The Israeli government has accused Hamas of staging the shootings to blame Israel. The government has accused Hamas of firing from food lines and filming it for propaganda videos. Hamas denies the accusations.

Meanwhile, Médecins Sans Frontières, or Doctors Without Borders, said on Friday that the number of malnutrition cases has reached an all-time high at two MSF clinics, one in Al-Mawasi in southern Gaza and one in Gaza City in the north.

In both clinics, more than 700 pregnant and breastfeeding women and nearly 500 children with severe and moderate malnutrition are enrolled in outpatient therapeutic feeding centers, according to the group.

"This is the first time we have witnessed such a severe scale of malnutrition cases in Gaza," Dr. Mohammed Abu Mughaiseb, MSF's deputy medical coordinator in Gaza, said in a statement. "The starvation of people in Gaza is intentional. It could end tomorrow if the Israeli authorities allow food in at scale."

Meanwhile, health care staff in Gaza are reporting that they have to operate without proper medical supplies due to shortages.

Doctors at Al-Helou Hospital in Gaza City, in central Gaza, said they are struggling to care for newborns and premature babies, many of whom are crammed into single incubators due to fuel shortages.

The head of the neonatal department at the hospital, Dr. Nasser Balbal, told Reuters the lack of functioning generators and electricity is paralyzing their services, leading to the death of patients in some cases.

"In the case when the generators stop ... the services are paralyzed and it leads to the death of some the cases due to the power outage, and this is caused by a fault in the electric generators, and from a shortage in fuel," Balbal said. "We call for electric generators to be provided and for fuel to be provided in sufficient quantities in order to continue providing services."

The United Nations warned that Gaza's fuel shortages have reached a critical level, leaving civilians and aid workers with an inability to power water systems, sanitation systems, hospitals, ambulances and other humanitarian operations.

"The United Nations agencies and humanitarian partners cannot overstate the urgency of this moment: fuel must be allowed into Gaza in sufficient quantities and consistently to sustain life-saving operations," a statement read in part.

It comes as a report from the NGO Physicians for Human Rights and the Global Human Rights Clinic at the University of Chicago Law School published this week found the Israeli government's restrictions on medical supplies entering Gaza "resulted in foreseeable, severe, and often preventable pain and anguish" to civilians seeking medical care.

Health care professionals volunteering in Gaza interviewed for the report said a lack of supplies, including morphine and scalpels, impacted their ability to provide proper medical care.

"These restrictions have imposed, effectively, almost medieval conditions on health care workers in Gaza," Saman Zarifi, executive director of PHR, told ABC News. "So, we heard about surgeries being performed without anesthesia, amputations of limbs in places where ordinary surgery should have been absolutely possible, untreated infections and patients with chronic illnesses going into terminal mode."

He continued, "So it's a really kind of a harrowing picture of totally unnecessary pain causing preventable deaths and lasting disabilities."

Zarifi said he believes Israel lifting some of the current restrictions in place on medical supplies could help Gazans receive the vital medical care they need.

The IDF did not immediately respond to ABC News' request for comment on fuel or medicine shortages being reported at hospitals or about the NGO report.

In a speech on Thursday in Washington, D.C., Prime Minister Benjamin Netanyahu said if Hamas does not agree to the conditions Israel has set for a permanent ceasefire in 60 days, the IDF will use even more force in Gaza.

Israel is calling for Hamas to lay down its weapons, for the group to have no more government or military capabilities and for Gaza to be demilitarized.

Hamas released a statement in response, calling Netanyahu's motives "malicious and ill-intentioned."

"The Movement had previously proposed a comprehensive exchange deal, under which all captives would be released in one phase, in return for an agreement that guarantees a permanent cessation of aggression, a full withdrawal of the occupation army, and the unimpeded flow of humanitarian aid," Hamas said in a statement. "However, Netanyahu rejected this proposal at the time and continues to evade and place further obstacles."

The war began on Oct. 7, 2023, when 1,200 people were killed in a Hamas-led surprise attack on southern Israel. Hundreds more were taken hostage. At least 20 living hostages are believed to still remain in Hamas captivity. Since the war began, over 57,000 people in Gaza have been killed, according to the Hamas-run Gaza Ministry of Health.

ABC News' Will Gretsky, Jordana Miller and Dana Savir contributed to this report.