Japan said on Friday that it could be afflicted by its first outbreak of the H5N1 bird flu strain in three years, as the disease killed an Indonesian woman and spread closer to Vietnam's largest city.

An official at a Jakarta hospital said on Friday that a woman had died of bird flu and four other people were being treated for symptoms for the H5N1 virus, which many scientists fear could mutate and trigger the next global flu pandemic for humanity.

The past week has seen a flare-up of infections, echoing past winters, the season when the virus appears to thrive.

About 2,400 chickens died on a farm in the Miyazaki area of southwestern Japan in the past three days, an outbreak that, if confirmed as the H5N1 bird flu virus, would be the first in Japan since 2004. There were no reports of human infections.

Masayuki Kunii, senior vice-minister at Japan's Agriculture Ministry, told reporters on Friday: "It's not confirmed at this point that it's the highly virulent influenza, but the chances remain very high."

Results of a simple preliminary test for the bird flu virus were positive, but agricultural officials said it might take several days to determine the exact strain of the virus.

Tests could show as early as Saturday whether the strain is the H5 or H7 subtype, but more time was needed to see whether it was the virulent H5N1 or less virulent H5N2 that was present.

In Vietnam, a government report said bird flu in poultry had moved closer to Ho Chi Minh City, the nation's largest urban area, after an outbreak was confirmed in a fifth province.

Source: Chiina Daily/agencies