A UN appeal to cope with Typhoon Haiyan has been increased from $301 to $348 million as the extent of the storm disaster becomes clearer.

UN humanitarian chief Valerie Amos said the death toll, increased Friday to 5,200, would rise higher even 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 told a news conference at UN headquarters after a trip to the Philippines.

Amos said huge numbers of people are still exposed to bad weather in the nine provinces ravaged by the storm. 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 the storm had also left a major communications blackout. "People have little or no access to basic information through cell phones, internet and radio, TV or newspapers," she said.