None of Gaza’s 36 hospitals are functional enough to treat critical trauma cases or perform surgery, the World Health Organization said on Monday, even as the number of people needing urgent medical treatment was rising daily among the enclave’s population of 2.2 million.

Michael Ryan, W.H.O. executive director, said in a video briefing that most of the hospitals were closed entirely, particularly in Gaza’s northern end, where Israel has focused its ground offensive. He said that of the 11 hospitals in the southern Gaza Strip, four were non-functional and the others could only provide basic services. They are more like community clinics rather than major hospital.

“The scale of injuries, the need for supplies, the inability to move around within the Strip and the inability to do that safely is a huge strain on all of the U.N. community and NGO community to serve the people on the ground,” He said.

Mr. Ryan spoke also of the Indonesian Hospital in Gaza’s northern region, which was hit by a deadly blast on Monday. He said the hospital could not accept any new patients and that its medical staff would likely request an evacuation in the near future.

The dire conditions for civilians and the high death toll in Gaza has drawn international criticism of Israel’s military response to the terrorist attacks Hamas launched from Gaza on Oct. 7. On Monday, the U.N. chief, António Guterres, who has repeatedly called for a cease-fire, said, “We are witnessing a killing of civilians that is unparalleled and unprecedented in any conflict since I have been secretary-general.” He was appointed to this post in 2017.

W.H.O. briefing Mr. Ryan stated that the loss to Al-Shifa hospital, which was taken over by Israeli forces last week, was a serious blow. The hospital provided cancer care and treatment as well dialysis services. It also offered trauma surgery and reconstructive surgeries. The W.H.O. briefing stated that the loss to humanity of Al-Shifa Hospital which Israeli forces took control last week is a serious blow as it had provided cancer, trauma, and reconstructive surgeries. “all of the complicated stuff you would expect of a very high-powered reference center.” Al-Shifa, Gaza’s largest hospital, has been a key part of the enclave’s health care system for 75 years.

Thirty-one premature infants were evacuated on Sunday after they had to leave incubators for lack of fuel. U.N. officials said that five more premature babies died. Monday, 28 people were transported to Egypt for medical treatment.

Rob Holden of the World Health Organization said that several hundred thousand civilians still remain in northern Gaza. The conditions present a significant challenge for providing them with emergency medical care. Senior emergency officer in Gaza who spoke via video on Monday at the briefing from the border of Rafah in Egypt.

The areas outside some of the hospitals — including Al-Shifa and Indonesian — were active battlegrounds, Mr. Holden said, and were a major focus of attention. Holden said the struggles faced by smaller hospitals were also crucial, as they are often the first point of contact for sick and injured patients.

This month, a medical worker treated injured children at Al-Aqsa Martyrs Hospital, Deir Al Balah in Gaza.Credit…Samar Abu Elouf, The New York Times

With the majority of Gaza’s population displaced, Mr. Ryan said, overcrowded shelters are struggling with poor hygiene, malnutrition and the approach of cold weather. In such conditions, the spread of disease will increase the burden of a health system that is already struggling to deal with new patients.

Ryan stated that southern Gaza is not safe, even though Israel had ordered the evacuation of civilians. More than a third of all deaths and injuries from Israeli airstrikes have been recorded in Gaza’s south, he said.

It is nearly impossible to evacuate patients from northern hospitals, and this could put some patients at risk. “huge danger,” Ryan stated that the medical facilities in southern states are not equipped to handle them.

“The care of oncology patients, the trauma care, the reconstruction surgery — many of those services are either only available or mainly available in those major hospitals in the north,” Mr. Ryan said.