AMMAN — More than 410,000 children across Iraq, Iran, Lebanon and Yemen have been pulled out of school by the war and the displacement it has triggered, the United Nations children’s agency said Sunday, warning that nutrition screening, vaccination coverage and protection services for minors inside the largest reception sites were deteriorating faster than humanitarian agencies could expand capacity.

In a regional situation report released simultaneously in Amman, Geneva and New York, UNICEF said it had verified the closure of 1,840 primary and intermediate schools across the four countries since March 1, including 612 sites in Iranian provinces along the Iraqi border, 437 in Lebanon south of the Litani, 318 in Iraq’s Anbar, Diyala and Sulaymaniyah governorates, and the remainder split between Yemen and the Jordanian receiving sites near Ruwaished. The agency estimated that an additional 160,000 children were attending sharply curtailed sessions, often two or three days a week, in buildings doubling as shelters.

“This is the largest single disruption to children’s lives in this region since 2014, and we are only five weeks into it,” said Adele Khodr, UNICEF’s regional director for the Middle East and North Africa, speaking at a briefing in Amman. “What worries us most is not the school numbers, alarming as those are. It is what is happening to the children who are no longer being weighed, no longer being vaccinated, no longer being seen by any adult outside their own family.”

Khodr said routine growth-monitoring visits, the principal early-warning system for child malnutrition in the region’s aid architecture, had fallen by 71 percent across the four countries compared with the first week of February. Measles vaccination coverage had dropped by half in southern Lebanon and by more than 60 percent in the Iranian-receiving camps around Sulaymaniyah and Penjwen. In Yemen, where a cholera outbreak that resurfaced in February has continued to spread through the western governorates, UNICEF said its oral rehydration teams were reaching roughly a third of the children they had screened a year ago.

The report drew particular attention to the situation inside the four expanded transit sites that Iraq’s Ministry of Migration and Displaced has stood up along the Iranian border since March 22. At Penjwen, the largest of the sites, a population that had been planned for 18,000 had grown to roughly 31,000 by Saturday, according to UNHCR figures cited in the UNICEF document. Tented classrooms erected by the Norwegian Refugee Council in late March have been repurposed as overflow sleeping space for unaccompanied minors and elderly arrivals; the daily children’s-protection caseload at the site has tripled in ten days.

“We registered fourteen unaccompanied children in a single afternoon on Thursday,” said Sarah Eliasson, a child-protection officer with the Norwegian Refugee Council working at Penjwen. “Two of them did not know what city they had come from. One little girl was carrying a phone number written on her forearm in pen, and the number did not work. We do not have the staff for this. We are running an emergency triage of children’s lives with the resources of a regular field operation.”

Inside Iran, UNICEF said its access remained limited to coordination with the Iranian Red Crescent and a handful of authorized local partners. Even so, the agency cited Iranian Health Ministry figures placing the number of school-age children displaced inside the country at more than 240,000, with the bulk concentrated in Isfahan, Yazd and Kerman provinces, where civilians from Khuzestan and Ilam have been moved inland on requisitioned buses. Iranian state television on Saturday aired footage of school dormitories in Yazd being converted into family shelters, with classes for resident students suspended through the end of the academic term.

The picture in Lebanon was described as the most acute on a population-adjusted basis. Lebanon’s Ministry of Education and Higher Education, in a statement issued late Saturday, said 437 schools south of the Litani River had been formally closed and that an additional 290 had moved to remote instruction, a modality complicated by extended blackouts and the partial collapse of the country’s internet backbone after Israeli strikes on a Hezbollah-linked logistics node near Baalbek on March 31. Education Minister Abbas Halabi said the ministry was preparing emergency catch-up programming for the summer if hostilities eased, but warned that “an entire cohort is at risk of losing the year if this war continues into May.”

Humanitarian officials interviewed Sunday said the educational disruption was already feeding measurable secondary harms. The International Rescue Committee, in a parallel statement, said its case-management teams in Jordan had documented a sharp rise in early-marriage inquiries among Syrian families newly displaced a second time into the kingdom, and that child-labor referrals at its Mafraq center had nearly doubled since mid-March.

“When schools close in this region, two things happen quickly,” said Hala Mansour, the Mercy Corps regional director who briefed donors in Geneva on Friday. “Girls disappear into early marriages their families would not have considered three months ago. Boys disappear into informal work that nobody is regulating. By the time the war ends, the damage on those two fronts is already done, and it does not reverse on the timetable of a ceasefire.”

The UNICEF report estimated the cost of a regional emergency-education and child-protection response at $640 million through the end of August, separate from the $1.4 billion supplemental appeal UNHCR and WHO issued a week ago. As of Sunday, donor pledges against the broader regional response stood at 38 percent of needs, with the United States, Germany, Japan, Qatar and the European Commission again leading commitments and a handful of Gulf states quietly increasing contributions through the Saudi Red Crescent.

A senior State Department official, speaking on condition of anonymity because internal deliberations were continuing, said the administration was preparing an additional emergency humanitarian package that would include a “significant” allocation for children’s services and that an announcement was expected before the end of the week. The official declined to confirm a dollar figure but said the White House had “heard the message” from European partners that civilian relief had lagged behind military expenditure.

In Islamabad, where mediators from Pakistan, Saudi Arabia, Egypt and Qatar continued informal consultations Sunday on the contours of a possible cease-fire framework, a senior Pakistani diplomat said a draft humanitarian annex now under discussion included specific language on the protection of children, schools and medical facilities. “If we get this annex right,” the diplomat said, “it will be the part of the agreement that survives the longest, regardless of how the rest of the talks land.”

Aid groups said they would press donors at the Geneva pledging conference, scheduled for the second week of April, to ring-fence a portion of any new commitments specifically for children’s services. UNICEF officials said an updated regional appeal incorporating Sunday’s findings would be presented at that meeting.