Health authorities in the central province of Nghe An have culled more than 2,365 chicken after many of them were found infected with two dangerous strains of bird flu.
The birds from two farms in Yen Thanh and Dien Chau Districts had not been vaccinated against avian influenza, according to Nghe An Animal Health Agency.
The agency also found a large numbers of fowl infected with the H5N1 and H5N6 viruses in Quynh Luu District and Vinh Town.
Nguyen Trong Bon of Dien Chau District Animal Health Agency said the district has banned chickens and ducks from being transported out of local farms.
Checkpoints have been set up and the agency has decontaminated local farms.
The central Preventive Health Department last week has warned about threats of bird flu spreading in the coming months due to cold weather.
The agency said the risks can be increased when more chickens and ducks are sold and consumed for the holiday seasons, particularly for the Tet Lunar New Year festival, which falls in February 2016.