Hanoi - Authorities in Vietnam said on Friday that bird flu had spread in two provinces in the southern Mekong delta, where massive outbreaks were first reported early this week.
Additional cases of the deadly H5N1 virus were detected in Ca Mau and Bac Lieu provinces, with nearly 8 300 poultry dead or culled, the national animal health department said on its website.
The two provinces were the first to report major outbreaks of bird flu in the communist nation within the past year. The virus had been identified in different locations in August but only a few storks were said to be killed.
"When poultry showed initial symptoms of bird flu, we culled them immediately without even waiting for the test results," said Dam Duy Thu, deputy head of the Bac Lieu provincial animal health department.
"We are closely monitoring the situation," he told AFP, adding that more than 160 poultry had been culled in Phuoc Long district on Thursday.
Authorities in the two provinces came under intense criticism by the agriculture ministry for failing to quickly detect and report the outbreaks.
Animal health officials in Ca Mau province refused to comment on Friday.
The ministry asked all local authorities to step up monitoring for outbreaks of avian influenza and warned officials they could face sanctions if all necessary measures were not taken.
"Local authorities and animal health workers are responsible for monitoring the epidemic situation. Local authorities will bear full responsibility for any late detection of the outbreaks," it said on its website.
Vietnam has reported no human cases of bird flu since November 2005. The disease has killed 42 people in the country between late 2003 and late 2005.