Malaysian authorities have mounted a 24-hour surveillance within 1 km radius of villages where birds were found dead with the deadly N5H1 virus while a strict watch is being kept on birds at the National Zoo in Kuala Lumpur.

A surveillance is also being maintained around a 10-km radius of the bird flu-hit areas in Setapak, outside Kuala Lumpur, to prevent the virus from spreading beyond the affected region, officials said Wednesday.

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Veterinary department workers have culled 900 chickens and ducks within the 1-km radius of the four affected villages and as a precautionary measure officials have taken fluid samples from 400 birds within and outside the area where the N5H1 virus was discovered.

Health experts have said those who lived or worked in close proximity to birds were at most risk. The infected birds excrete the virus in their faeces, saliva and nasal secretions.

Meanwhile, the National Zoo's bird enclosure has been closed to the public due to the avian flu threat, the Star newspaper said.

Visitors to the zoo and their vehicles are being disinfected to prevent any virus from being brought into the compound.

The zoo is only a 10-minute drive from the area where 40 chickens died of the H5N1 virus.

Zoo officials are worried that there are 300 free-flying birds that consider the zoo their home.