BANGKOK/HANOI, Jan 24: UN officials said on Saturday the deadly bird flu that has jumped to humans in Vietnam and Thailand was spreading - a warning grimly underlined by confirmation of a sixth death from the disease.

Experts fear the avian virus could set off an epidemic worse than SARS, another disease which crossed from animals to humans, killed 800 people and frightened the world last year.

"There's no denying the disease is spreading," Anton Rychener, Vietnam representative for the Food and Agriculture Organization, a U.N. body, said.

The World Health Organization said a 13-year-old Vietnamese boy had died on Thursday from the H5N1 strain of avian flu, and that an eight-year-old girl had tested positive for the virus.

She was critically ill in Ho Chi Minh City, the first confirmed cases of bird flu in southern Vietnam since four children and one adult died in the country's north.

In Thailand, a chicken butcher, one of six Thais being tested for the disease, is believed to have died of pneumonia on Friday.

The WHO has said the simultaneous outbreaks in Japan, South Korea, Vietnam, Thailand and Cambodia were "historically unprecedented".-Reuters