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DHAKA, April 11 (Reuters) - Bird flu is spreading among poultry in Bangladesh despite persistent efforts by veterinary and health personnel to contain it, fisheries and livestock ministry officials said on Wednesday.

"The avian virus has been detected in three more farms in southern Noakhali, northern Gaibandha and western Jessore districts," said a spokesman of the ministry's livestock department, who declined to be named.

Jessore and Gaibandha districts are close to the Indian states of West Bengal and Assam respectively, where bird flu broke out much earlier, officials said.

Mohammad Abdul Motalib, s senior official of the livestock department, said the H5N1 virus spread despite a struggle by hundreds of veterinary and health officials to hold it in check.

Movement of chickens had been banned outside a 10 sq km (3.9 sq miles) area around affected farms.

Nearly 77,000 chickens have been culled so far from 30 farms since the outbreak of avian flu was confirmed simultaneously in six farms at Savar near Dhaka on March 22.

Nearly 600 workers at the infected farms have been given a local version of the Tamiflu anti-viral drug as a precaution, Health Ministry officials said.

The government says it has sufficient Oseflu, the local version of Tamiflu, produced and marketed by a Bangladesh company since last year.

No humans have tested positive for the disease in densely populated Bangladesh.

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.

Bangladesh 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.

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