New Delhi - Authorities in India's north-eastern Assam state culled 40,000 poultry of some 60,000 infected birds ordered to be killed after an outbreak of bird flu in the state, a news report said Monday.

Culling operations have been mounted in nearly 50 villages of central Kamrup district since Friday and 40,000 chickens and ducks have been killed, Manoranjan Choudhury, an official of the state veterinary department, told the IANS news agency.

The culling operations are expected to be completed by 22 teams in the next three days.

India's Health Ministry last week confirmed the outbreak of bird flu after laboratory tests found strains of the deadly H5N1 avian influenza.

Meanwhile, the government in the eastern state of Orissa sounded an alert and asked agencies to take measures to prevent a similar outbreak after bird flu hit Assam.

India has so far seen four major outbreaks of bird flu, but has not yet reported any cases of human infection.

An earlier outbreak in eastern India in January was described as the worst outbreak in the country so far by the World Health Organization.

H5N1 mainly affects poultry and wild birds, but can infect humans who have close contact with sick fowl.

Scientists fear that if it spreads unchecked, the disease could mutate into a form which could be transmitted between humans, leading to a worldwide pandemic.