DHAKA (AFP) - Bangladesh has slaughtered 50,000 more poultry to combat a severe outbreak of bird flu that continues to spread while neighbouring India has stepped up similar efforts, officials said.

The birds were killed near the capital Dhaka as the deadly H5N1 strain spread to a new district. The virus is now present in 35 of Bangladesh's 64 districts, the livestock department said.

"On Sunday, the flu was detected in 10 new farms, forcing the livestock department to slaughter all the birds in the area," livestock department scientific officer Biddyut Kumar Das said.

Efforts to slaughter birds in the western Kushtia district would continue on Monday, Das said. "The situation is not good. There is no sign of improvement."

The department said nearly 50,000 birds were slaughtered on Sunday in the single biggest cull since the deadly virus was detected on a farm near Dhaka in February last year.

No human infections have been reported in Bangladesh since the latest outbreak began last month, but a health official said nearly 800 farmers had been given anti-viral drugs as a precaution.

The government has also ordered major hospitals to set up isolation units.

"We've also confined several people in their homes," government spokesman Mahmudur Rahman said on Saturday.

In India, which has been combating its third and worst outbreak of the virus among poultry, three poultry-culling workers were in isolation after developing flu symptoms, officials said in West Bengal state, which borders Bangladesh.

Officials in the eastern Indian state, where three million chickens have been slaughtered since the virus was confirmed in dead birds last month, said no human cases had been reported as the virus spread to 13 of 19 districts.

Health workers in West Bengal accompanied by police on Monday began house-to-house searches to find hidden birds within the infected zones.

The United Nations Food and Agriculture Organisation has said that Bangladesh also needs house-to-house surveillance to fight the spread of bird flu.

Bangladesh is the world's most densely populated country, with nearly 1,000 people per square kilometre (2,600 per square mile).

Experts fear bird flu could mutate into a form easily passed from human to human.