Unrwa
The UN World Food Programme has said it has enough food ready to feed more than a million people for three months.
The agency provides nearly the entire population of the coastal enclave with basic supplies and needs access through Israel.
Gaza's emergency service said its operations had come to a halt because of the three-week Israeli assault into northern Gaza.
UNRWA staff report that they cannot find food, water or medical care, Commissioner-General Philippe Lazzarini wrote on X.
Israeli forces have destroyed homes and schools serving as shelters, leaving many civilians with no refuge as winter approaches.
WFP distributed its last remaining food stocks in the north to partners and kitchens sheltering newly displaced families, but these are barely enough to last two weeks.
The parents who have come to the health centre are well aware of the importance of vaccinations.
According to the UN agency for Palestine refugees, UNRWA, these new evacuation orders now cover approximately 84 per cent of the Gaza Strip.
The UN agency and partners remain on the ground to provide essential services and supplies to support and protect children.
To date, no one has been treated in Gaza for paralysis or other symptoms caused by poliovirus infection.
Since war erupted nine months ago between Israel and Palestinian group Hamas in Gaza, U.N. officials have stressed UNRWA is the backbone of aid operations.
Israeli forces continued to press their offensive in north and central Gaza on Wednesday, and deepened their incursion into two Gaza City districts, carrying out house-to-house searches.
A medical source said 40 had been killed, including 14 children and nine women.
The small city on the southern edge of the Gaza Strip had been sheltering more than a million Palestinians who fled Israeli assaults on other parts of the enclave.
"There are reports of mass casualties, including children and women, among those killed. Gaza is hell on earth,” the UN organisation said.
UNRWA said in a statement on X that only seven out of its 24 health centres were operational and that it had not received any medical supplies in the past 10 days due to "closures/disruptions"
Fowler underlined UNRWA’s mandate to provide services to Palestine refugees, which includes healthcare, education and social support.
The heads of the WHO, the UN rights office, UNICEF and the World Food Programme, warned defunding UNRWA risked a "catastrophic" humanitarian collapse in Gaza.
Around 5.9 million Palestinians are registered with UNRWA and can access health care, social services, microfinance and emergency aid.
The countries are the US, Australia, Britain, Canada, Finland, France, Germany, Italy, Netherlands and Switzerland. They have welcomed investigation into the allegations that some UNRWA staff took part in Hamas's October 7 attack.
A number of donor countries -- including Australia, Britain, Finland, Germany and Italy -- on Saturday followed the lead of the United States in suspending additional funding to UNRWA.
Donors including the US, Germany, Britain, Italy, Australia and Finland suspended additional funding to UNRWA.
The UN said some 30,000 people are sheltering at the site and the death toll could be higher.