Bird flu has spread to another district in Bangladesh forcing authorities to cull 3,000 more chickens over the last two days, officials said on Sunday.
The infected chickens were found at a farm in Dinajpur district 450 km northwest of the capital Dhaka.
With the latest cull, some 160,000 chickens have now been slaughtered and 1.5 million eggs destroyed on 62 farms in 12 districts since the virus was first detected at six farms at Savar near Dhaka in March.
There have been no reported cases of human infection.
More than 100,000 farms have been inspected and some 125 million chickens vaccinated since the outbreak emerged, a fisheries and livestock ministry statement said.
The World Bank last week pledged more than $ 30 million to a Bangladesh project to fight bird flu until 2012.
Earlier last month the United Nations Food and Agriculture Organisation (FAO) said Bangladesh needed a long-term strategy to control the H5N1 strain of bird flu.