The World Health Organization and the leaders of 15 United Nations and humanitarian organizations "urge, yet again, all parties fighting in Gaza to protect civilians, and call on the State of Israel to cease its assault on Gaza and on the humanitarians trying to help," in a joint statement Friday.

The WHO called the situation in North Gaza, "apocalyptic," warning, "The entire Palestinian population in North Gaza is at imminent risk of dying from disease, famine and violence."

"Hospitals have been almost entirely cut off from supplies and have come under attack, killing patients, destroying vital equipment, and disrupting life-saving services. Health workers and patients have been taken into custody. Fighting has also reportedly taken place inside hospitals," the groups said.

"Dozens of schools serving as shelters have been bombed or forcibly evacuated. Tents sheltering displaced families have been shelled, and people have been burned alive. Rescue teams have been deliberately attacked and thwarted in their attempts to pull people buried under the rubble of their homes," the groups said.

Hamas does not support the cease-fire agreement proposed by Egypt -- a temporary cease-fire agreement that included a prisoner-hostage exchange and an increase in aid -- a Hamas political official said in an interview with Al Jazeera.

The Hamas official said the agreement doesn't include a permanent stop in fighting, a withdrawal of the Israeli occupation from the Gaza Strip nor does it allow for the return of the displaced.

The proposals do not address civilians' need for security, relief, reconstruction or opening the crossings, especially the Rafah crossing, the official said.

Any offer or agreement must stop the Zionist aggression permanently and not temporarily. The occupation is trying to exploit the assassination of resistance leaders to show that the resistance has been broken and the truth is that the resistance is increasing its strength, the official said.

The Israel Defense Forces said it killed Izz al-Din Kassab, a member of Hamas' political bureau and head of national relations within the organization, in a strike in the area of Khan Yunis.

"Kassab was one of the last high-ranking members of Hamas' political bureau alive in the Gaza Strip. Alongside him, his assistant, the militant Ayman Ayesh, was also eliminated," the IDF said in a statement Friday.

The third phase of the polio vaccination campaign is set to begin in part of the northern Gaza Strip on Saturday. It had been postponed from Oct. 23 due to lack of humanitarian pauses and intense bombardment of the strip.

"These conditions made it impossible for families to safely bring their children for vaccination and for vaccination teams to perform their duties. The humanitarian pause necessary to conduct the campaign has been assured, however, the area of the pause has been substantially reduced compared to the first round of vaccination in northern Gaza, conducted in September 2024," UNICEF and the World Health Organization said in a statement.

But, WHO and UNICEF warned that it will be difficult to interrupt poliovirus transmission because "at least 90% of all children in every community and neighborhood must be vaccinated, which will be challenging to achieve given the situation."

"The campaign in northern Gaza follows the successful implementation of the first two phases of the second round in central and southern Gaza, which reached 451,216 children -- 96% of the target in these areas. A total of 364,306 children aged between 2 and 10 years old have received vitamin A so far in this round," the WHO and UNICEF said.

-ABC News' Nadine Shubailat