DHAKA -- Bangladesh needs house-to-house surveillance to fight bird flu because the situation has worsened and is "posing a danger to public health," the Food and Agriculture Organization (FAO) said Thursday.

The statement from the UN's FAO came as neighboring India battled its worst outbreak of bird flu -- believed to have spread from Bangladesh, which has been reporting sporadic outbreaks of the deadly H5N1 strain since February 2007.

"The situation has worsened in the past week compared to the first few months of the outbreak. The international community is very concerned," FAO's Bangladesh chief Ad Spijkers told Agence France-Presse in Dhaka.

"We took the concern to the minister Wednesday and donors are going to meet with the government very soon to discuss comprehensive measures to fight the disease. It's posing a danger to public health," he said.

"The government should do active house-to-house surveillance to control the disease," he said.

No human infections have been reported in Bangladesh, but Spijkers' remarks came amid a rise in outbreaks in the country's southern, central and northern districts. The government said more than 20,000 birds were slaughtered in the past week.

Bangladesh border security forces were put on high alert Thursday to stop the transport of poultry from India's West Bengal state, where authorities are struggling to control a massive bird flu outbreak.

Since Bangladesh's first bird flu outbreak, the disease has been detected in 26 out of the country's 64 districts, prompting authorities to slaughter at least 355,000 birds.

Officials said the situation has worsened in the past week but the disease remains contained in the impoverished country of 144 million people.

"We don't think the situation is as bad as in West Bengal," said Salahuddin Khan, livestock department director.

Experts differed, saying the situation was far worse than the government claims, with farmers holding back from reporting many cases.

"Bird flu is now everywhere. Every day we have reports of birds dying in farms," M.M. Khan, leading poultry expert and the treasurer of Bangladesh Poultry Association, said last weekend.

The situation was serious and public health was in danger, Khan said.

"The government is trying to suppress the whole scenario."

Bangladesh has been under emergency rule since January 2007 following months of strikes and rioting by rival supporters of the country's two main political parties. The government has promised to clean up the country's notoriously corrupt political landscape before holding elections in late 2008.

The FAO country chief said the world's most densely-populated nation faced a "delicate situation" since the poultry industry employs five million people.

"It's tough to impose movement control in a small country populated by more than 144 million people. It has become a sensitive and difficult issue as the livelihoods of a lot of people depends on birds," Spijkers said.

The poultry industry here has about 220 million chickens and 37 million ducks.

Experts fear the H5N1 strain could mutate and become able to pass between humans.