The UN says 1.5 million children are at risk of malnutrition in typhoon-ravaged areas of the Philippines as it calls for greater efforts to provide food and water.
A UN appeal to cope with Typhoon Haiyan's devastation has also been revised from $301m to $348m as the extent of the storm disaster becomes clearer.
Valerie Amos, UN humanitarian chief, said the death toll had risen to 5,235, with 1,613 missing, and would rise higher as the spotlight turns away from the November 8 super typhoon.
"I am very concerned that some 1.5 million children are at risk of acute malnutrition and close to 800,000 pregnant and nursing mothers need nutritional help," Amos said on Friday at the UN headquarters in New York City after a trip to the Philippines.
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Amos said huge numbers of people are still exposed to bad weather in the nine provinces devastated by Haiyan.
An estimated four million people have been left homeless.
A huge international relief operation was launched after the storm, but Amos said: "Much more needs to be done. Food, clean water and shelter remain the top priorities."
The death toll has mounted as rescuers reach remote islands and areas hit by fierce winds and huge waves in one of the biggest storms ever recorded.
Amos said Haiyan had also left a major communications blackout.
"People have little or no access to basic information through mobile phones, internet and radio, TV or newspapers," she said.
The World Bank on Friday added $480m in emergency aid to the Philippines, taking its support to nearly $1bn.
The Asian Development Bank has also offered $500m concessionary loans.