The humanitarian crisis gripping millions of Somalis due to a harsh drought this year will persist for the coming months, the UN said Tuesday as it appealed for $1.5 billion for 2012.

The UN declared six regions in southern Somalia famine zones earlier this year, and although it said last month that three regions were now not facing famine, more than half of Somalia's 10 million people are in dire need of help.

"The Somalia crisis is everybody's responsibility and Somalis need support now. We cannot afford to wait or we will let down the Somali people," said Mark Bowden, the UN humanitarian coordinator for Somalia.

"The $1.5-billion (1.14-billion euro) appeal is based on a realistic assessment of the emergency needs of four million people in crisis, tens of thousands of whom will die without assistance."

Relentless conflict since 1991, drought and insecurity have plunged Somalia into the world's worst humanitarian crisis.

Donors contributed more than $800 million (606 million euros) of the one billion dollars requested this year to help some 12 million people affected by East Africa's worst drought in decades.