The World Health Organization says an outbreak of bird flu among chickens in Vietnam may be linked to the deaths of 10 people. The bird flu has also sickened and killed thousands of chickens in South Korea and Japan.

The United Nation's health agency said Monday that nine children and one adult hospitalized with an influenza-like illness in Vietnam since last October have died. Two others have been hospitalized with similar symptoms.

The World Health Organization is now investigating a possible link between the deaths and the bird flu, which has led to the deaths of hundreds of thousands of chickens in Vietnam, South Korea and Japan.

"The first hospital admission goes back to October 28 last year the most recent admission was January 5 this year," said Peter Cordingly, the WHO's regional spokesman. "Samples from some of the people who have fallen ill in the Hanoi region have been sent overseas for examination."

A WHO official in Vietnam says the small number of patients over three months means the disease is not spreading rapidly.

So far, less than 100,000 chickens have been culled in Vietnam but the WHO estimates roughly 600,000 chickens have shown signs of the bird flu.

Mr. Cordingly says the bird flu strain found in Vietnam and South Korea is similar to the H5N-1 virus, which jumped from chickens to infect and kill six people in Hong Kong in 1997.

That outbreak was the first time a bird flu virus is known to have jumped directly from birds to humans. To contain the deadly disease, Hong Kong slaughtered all live poultry in the city, winning praise from international health experts for possibly averting a wider outbreak.

Last year, Hong Kong reported two more imported bird flu cases in humans. Both patients died. Doctors say the two had visited chicken farms in China.

In the past several weeks, more than a million chickens and ducks in South Korea either died from the flu or were slaughtered to contain the spread of the disease. Japan confirmed on Monday that around 6,000 chickens in the country's south have died of flu.

Mr. Cordingly says WHO epidemiologists are investigating if migratory birds are spreading bird flu to different countries.