The United Nations appealed on Sunday for nearly $450 million (289 million pounds) in humanitarian aid for conflict-torn Yemen to save it from becoming what one U.N. official called another Somalia.

Yemen will need substantial humanitarian assistance over the next three to five years, especially for food, health care, sanitation and clean water, U.N. agencies and other relief groups working in Yemen said at a conference in Dubai.

The Yemen Humanitarian Response Plan 2012 is seeking $447 million. This represents an increase of 95 percent compared to one year ago, they said, adding the money would be targeted to help around 4 million vulnerable people.

Almost a year of protests against outgoing President Ali Abdullah Saleh has brought Yemen's economy close to collapse, worsening already dire living conditions for many people who face acute shortages of fuel, food, water and electricity.

The situation is dramatic. If we don't act now, we hit a humanitarian disaster soon, said Geert Cappelaere, representative of the U.N. Children's Fund (UNICEF) in Yemen.

If we don't act now, Yemen will become another Somalia from a humanitarian perspective.

Cappelaere said more than 30 percent of Yemeni children were acutely malnourished.

In general, when you have 15 percent of under-five-year-olds that are acutely malnourished, we call that a nutrition emergency. In Yemen, you have twice the emergency level.

COMPLEX CRISIS

Aside from its political and economic crisis, Yemen must also cope with a growing influx of refugees from the Horn of Africa to its southern coast and a host of Yemenis forced to flee their homes by fighting in the south and the north.

The U.N. High Commissioner for Refugees (UNHCR) estimated that at the end of November around 214,000 refugees and almost half a million internally displaced persons were in Yemen.

Arrivals from Somalia had increased, with 3,292 reaching Yemen in September and 3,689 in October, compared to a monthly average of 1,648 in the first half of the year, UNHCR said.

This year's turmoil in Yemen had posed many challenges, the country's health and population minister, Ahmed al-Ansi, said.

The humanitarian situation in Yemen is very precarious at the moment, he told Reuters. It affects all parts of life of citizens, not just health, but their economic activity, the environment, social life.

Saleh last month signed a pact brokered by Yemen's wealthy Gulf Arab neighbours to hand power to his deputy Abd-Rabbu Mansour Hadi.

Under the deal, Saleh's General People's Congress and opposition parties agreed to divide cabinet posts between them, forming a unity government to lead Yemen to a presidential election in February.

What has happened in the last 10 months has put the clock in Yemen back 15 to 20 years when it comes to the development and basic services, which were already not that widespread throughout the country, UNICEF's Cappelaere said.

What is now needed is a government that will make it a top priority not only to get the political side of things right, but also to give top priority for its development and the children.

The International Monetary Fund approved a $370 million loan for Yemen in August 2010, but only one disbursement of around $50 million has been made so far.

Aid officials urged Gulf countries to chip in more.

The bulk of donor money comes from Western countries. It's time that Gulf countries deliver as well, said Naveed Hussain, UNHCR's representative in Yemen.

(Reporting by Martina Fuchs; editing by Sami Aboudi and Alistair Lyon)