The bird flu crisis is affecting the poultry trade across the region

Experts are trying to establish if nine other deaths in Vietnam were caused by the virus and if two sick children also have it.

Various countries have announced bans on the import of live birds from affected areas.

And South Korea has confirmed its first case of the virus in birds for a week.

By far the most serious outbreak has been in Vietnam where experts from the World Health Organization (WHO) have confirmed that the deaths of two children and an adult were caused by the H5N1 virus, which is the same as that found in the sick chickens.

But at the moment health officials are playing down fears of an epidemic of bird flu- or avian flu - among humans.

"The evidence to date is that there is no sign of human-to-human transmission," said Dr. Shigeru Omi, the WHO's regional director for the Western Pacific in Manila.

"However, should this occur, we would have a serious situation. We are principally worried about the possibility that the avian virus could acquire full capability to transmit from one person to another," he said.

Vietnam confirmed it had an outbreak of the illness among chickens last week and it is thought that around one million birds have died, with thousands of others being culled to try and prevent the spread of the disease.

Hanoi has appealed for more international help to confront the crisis.

More experts from the WHO are on their way to the country as well as an expert from the World Food and Agriculture Organisation (FAO).

"We were officially requested this morning by the Ministry of Agriculture and Rural Development to help tackle the virus," said Anton Rychener, FAO representative in Vietnam.

Anxiety

South Korea's announcement of a new case has dashed hopes that the outbreak there was subsiding.

The Agriculture Ministry said the case was found at a farm in Yangsan, south-east of Seoul, and all chickens within three kilometres of the area will now be killed.

After an outbreak in December, South Korea is thought to have already culled two million chickens and ducks.

It is now thought that over 8,000 chickens have died from an outbreak of the disease in Japan's Yamaguchi prefecture in the south west of the country.

The prime minister, Junichiro Koizumi, said that he has ordered the agriculture minister "not to create anxiety for the people over the case."

Thailand, meanwhile, has declared itself free of bird flu, but it has admitted that it is trying to contain the spread of a strain of poultry cholera, which has forced it to destroy hundreds of thousands of chickens since November.

Imports

The outbreak of bird flu is also affecting trade between the region's nations.

Taiwan has banned all imports of live birds from Japan and Cambodia has stopped imports from neighbouring countries and sent experts to its poultry farms.

Hong Kong has announced a ban on imports from the three affected countries.

It has also said it would vaccinate all poultry coming into the territory by the end of this week

Hong Kong imports 70,000 live birds a day from mainland China, which has said that it is free from the disease.

Hong Kong was the first place where bird flu was thought to have transferred to humans, after six people died from the H5N1 virus in 1997 and 1998.