Three Vietnamese die of bird flu

There have already been cases of bird flu in Vietnam's poultry

The World Health Organization says there have been three new deaths from bird flu in Vietnam.

They mark the first officially confirmed cases of the disease since an outbreak in the region last February.

Hanoi has confirmed that at least one of the deceased was infected with the H5N1 strain of the virus, the WHO said.

The H5N1 strain is the only one known to jump directly from birds to humans, and claimed the lives of eight Thais and 16 Vietnamese earlier this year.

The WHO now says it needs to know whether these fresh cases of bird flu are a new outbreak or connected to the previous one.

The three cases were among a group of patients admitted to hospitals in Vietnam during July and August, and who have since been under close investigation by the health authorities.

The BBC's correspondent at the WHO headquarters in Geneva, Imogen Foulkes, said the knowledge that at least one of those who died was infected with the species-jumping H5N1 strain will alarm countries across Asia.

Since July, both Vietnam and Thailand have been reporting cases of infected poultry stocks, but until now, there were no confirmed reports of human infections.

Tens of millions of chickens have been destroyed in an effort to prevent the disease from spreading.

The WHO plans a thorough investigation of the deaths in Vietnam, including further analysis of the virus and checks on the working environment of the three people who died.

All those who may have been in contact with the victims will be checked for signs of the disease.