(Updates with Nepal alert)

By Biswajyoti Das

GUWAHATI, India, July 27 (Reuters) - Veterinary workers in protective clothing broke the necks of thousands of chickens on Friday, while medical staff checked people for flu symptoms to contain an outbreak of bird flu in poultry in India's northeast.

The outbreak of avian influenza in chickens this month on a small farm in the remote state of Manipur was the first in India this year, making it the 25th country to report the occurrence of the H5N1 strain in 2007.

Nearly 10,000 chickens have been killed in and around Chingmeirong village on the outskirts of Imphal, the state capital, before being thrown -- along with eggs -- into huge pits that were then covered with lime and salt and finally with soil.

Authorities plan to kill 150,000 birds by next week within a 5 km (3 mile) radius of the village.

India's Animal Husbandry Commissioner S.K. Bandyopadhyay said officials had stepped up the collection of blood and tissue samples from poultry from the country's northeast to see if there were more cases of farm fowl being infected with the virus.

Three other states in the region asked veterinary workers to visit farms to monitor the health of the birds, with two of them -- Assam and Nagaland -- putting up checkpoints on roads next to their borders with Manipur to prevent the entry of fowl from the affected area.

"All district officers have been asked to visit poultry farms and strictly implement bio-security measures," said A.K. Kotoky, director of Assam's veterinary and animal husbandry department.

Officials said there were no reported suspected human cases in Manipur, which borders Myanmar.

Nepal ordered quarantine posts and custom points along its border with India to be on alert, and asked importers to not bring poultry into the country, officials in Kathmandu said.

CITIZENS TAKE INITIATIVE

Officials said they would question thousands of people around the affected area on whether they were suffering from flu symptoms and had contact with poultry.

Volunteers distributed surgical masks on the streets of Imphal, while some kept watch on trucks and three-wheeler vans to stop smuggling of poultry from the affected area.

In some neighbourhoods near the affected farm where medical teams had not yet visited, anxious residents opened camps and asked those suffering from fever to report for checks.

Officials say the outbreak in Manipur seemed isolated.

Imphal is about 1,700 km (1,000 miles) from New Delhi, and closer to Bangkok than to the Indian capital.

Since 2003, a total of 192 people have died out of 319 people infected by the virus across the globe, the World Health Organisation says.

H5N1 remains largely a bird virus but experts fear it might mutate into a form that easily passes between people, triggering a pandemic in which millions could die.

In Manipur, some poultry farmers had stopped feeding fowl.

"We are scared to go near them," said Rajiv Singh, a poultry farmer near Imphal.

India's northeast, connected to the rest of the country by a tiny strip of land, neighbours Bangladesh, Myanmar and China, all of which have been hit by bird flu of the H5N1 strain.

Indian troops on the state's border with Myanmar have stepped up patrols to prevent poultry smuggling.

Last year, India faced two major outbreaks of the H5N1 strain in chickens in the west of the country. (Additional reporting by Gopal Sharma in Kathmandu)

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