YAOUNDE (Reuters) -- UN aid agencies asked donors on Monday for $47 million to help more than 1 million vulnerable people in Central African Republic, where raids by armed gangs near the border with Chad have compounded food shortages.

"Today, average life expectancy in the country is estimated at 38 years, and continues to fall at a rate of six months every year," said Joseph Foumbi, resident representative of UN children's fund UNICEF and humanitarian coordinator.

"Most of the people live on less than $1 a day. There is little food. Even cassava, the most basic foodstuff in the local diet, is often scarce," Foumbi told reporters.

Foumbi and other UN officials traveled from the country's dilapidated capital Bangui to Yaounde in neighboring Cameroon, where most of the diplomats accredited to Central African Republic are based.

He painted a dismal picture of the humanitarian situation, saying many children suffer from severe or chronic malnutrition.

In some areas hungry people eat toxic mushrooms and wild roots even though they know the risks, he said.

Elsewhere, water is scarce and hygiene poor with most villages lacking safe drinking water, exposing the people to preventable water-borne diseases.

Tuberculosis and HIV/AIDS were spreading, and infant and maternal mortality are common, he added.

Central African Republic has been racked by army mutinies and armed uprisings in recent years while the economy has suffered and civil servants are owed up to 44 months' pay. -------------------Attacks in north

Aid workers said the worst hit areas were in the north, where UN refugee agency UNHCR said 2,800 people fled over the border into Chad last week alone to escape attacks those fleeing blamed on armed bandits, rebels or the army itself.

UNHCR quoted Chadian authorities and witnesses saying at least 50 civilians were killed last week in Central African Republic. Around 50,000 Central Africans have taken refuge in Chad during a series of conflicts in the border area.

With a population estimated today at 3.9 million, CAR is one of the poorest countries in the world.

Some 73 percent of the population live below the poverty line, and the 2005 UNDP human development index ranks the country 171 of 177 countries surveyed.

Last year a similar humanitarian appeal for $27.5 million raised just $8.5 million, and much of that from the same U.N. agencies that made the "consolidated appeal".

The money is intended to improve agriculture, emergency food supplies, health, education, water management, law and order and other areas.

"We have to act now to prevent the further loss of human life, to prevent an already bad situation from getting worse," said Sopie de Caen, coordinator of the UN system in Cameroon.