Vietnam stepped up culling poultry on Saturday in a southern province where a woman was confirmed to have died of H5N1 bird flu, the same strain that killed 24 people in Asia earlier this year.
Vietnam's health ministry said two other people had also died of bird flu and it has more suspected cases in hospital. The two from northern Ha Tay province were a 4-year-old boy and an 11-month-old girl who died in early August.
"We have destroyed the poultry around the places of the victims," said a health official in southern Hau Giang province, where 25-year-old Pham Thi Nha Tuc died, becoming the first confirmed human victim since the H5N1 strain resurfaced last month.
State media said Hau Giang has culled nearly 17,000 chickens and birds in the past month.
The H5N1 strain killed 16 people in Vietnam and eight in Thailand earlier this year and outbreaks of bird flu have hit poultry farms in several countries in Asia in recent weeks.
The fresh outbreaks have re-ignited fears the illness could sweep across Asia just months after a mass culling campaign of tens of millions of poultry.
So far news of the outbreak and humans deaths in Vietnam has come through UN agencies. Vietnam's Health Ministry has held no briefings for foreign media and the ministry's Web site - www.moh.gov.vn - contains no information about the crisis.
Health officials in Hau Giang said four people including Tuc had died in the province with high fever and respiratory problems. Hau Giang is about 170 km (106 miles) south-west of Ho Chi Minh City, Vietnam's largest population centre.
Provincial officials have been culling poultry in Hau Giang since fresh outbreaks were first detected in early July but have stepped up the programme since the human deaths and are also disinfecting residential areas and farms.
The country's prime minister issued a directive this week banning the transport and trading of poultry from any infected area.
The World Health Organisation said samples from the two children who died of bird flu in the north were still being tested.
More patients from the northern and southern parts of the country were being tested, the WHO said.