Bangladesh said on Saturday bird flu has spread to six more farms despite efforts to tackle the virus by veterinary and health officials and the United Nations Food and Agriculture Organization.
"The infection was detected at a farm in western Magura district 200 km (125 miles) west of the capital Dhaka and five farms at Savar in the Dhaka district," a spokesman at the fisheries and livestock ministry said.
The H5N1 bird flu virus has been spreading in poultry flocks in Bangladesh ever since it was first detected on six of the country's farms on March 22 and despite culling and banning of the movement of chickens in areas with confirmed outbreaks.
Magura district is adjacent to India's West Bengal state of India, where bird flu was detected earlier.
Bangladesh also shares a border with Myanmar, which is fighting the disease. But no one knows for sure how the disease jumped to Bangladesh this March.
A 10-member FAO team arrived in Dhaka last week and has visited a number of affected farms and laboratories.
Since the detection of the H5N1 virus on March 22, some 98,000 chickens have been culled on 38 farms in nine districts.
No humans have tested positive for the disease.
The virus is known to have infected nearly 300 people in 12 countries since 2003, killing more than half of them.
Human cases of bird flu have generally been linked to contact with infected poultry. Health experts fear the virus may mutate into a form that passes easily from human to human, causing a pandemic that could affect millions.
The country has 125,000 small and large poultry firms producing 250 million broilers and six billion eggs annually. About four million Bangladeshis are directly or indirectly associated with poultry farming.