An outbreak of bird flu at a poultry farm in eastern England was confirmed Tuesday as H5N1 — the same virulent strain that has killed scores of people around the world.

Bird flu's return to Britain — weeks before the Christmas holidays — is a yet another blow to Britain's farmers, already struggling after herds were hit this year by foot-and-mouth and bluetongue.

Thousands of free-range turkeys, ducks and geese were being culled at a farm in Redgrave in the county of Suffolk, about 130 kilometers (80 miles) northeast of London.

The source of the outbreak has not yet been identified but was closely related to the strains found in the Czech Republic and Germany earlier this year, acting Chief Veterinary Officer Fred Landeg said.

If the bird flu spreads, it could devastate the hugely profitable Christmas trade in poultry.

A 3-kilometer (2-mile) protection zone and a 10-kilometer (6-mile) surveillance zone were set up around the infected farm, and further restrictions were imposed over Suffolk and much of the neighboring county of Norfolk.

The alarm was raised Sunday after a rise in death rates among birds owned by poultry producer Gressingham Foods, based in Woodbridge, Suffolk.

Landeg said Britain had successfully contained an outbreak of H5N1 earlier this year in Suffolk that led to the culling of 160,000 turkeys.

"With respect to this outbreak, there is still some uncertainty. We are at a very early stage of the investigation, and no two outbreaks of disease are ever the same," he said.

Bird flu has killed or prompted the culling of millions of birds worldwide since late 2003, when it first began ravaging Asian poultry stocks. It has killed at least 206 people worldwide since 2003.

Experts believe most victims were probably infected through direct contact with sick birds.

Bird flu is difficult for humans to catch but experts fear it could mutate into a form that spreads easily among people, potentially sparking a flu pandemic.

In Europe, H5N1 has previously been found in France, Switzerland, Germany and elsewhere. Human cases have been recorded in Turkey and Azerbaijan.

Britain's first case of H5N1 was in a swan in Scotland in 2006. In April 2006, chickens on a farm in Norfolk tested positive for the H7 subtype of the virus.

International experts said it was not surprising that more H5 had been detected in Britain, particularly since surveillance systems worldwide are now geared to spot the virus.

"The more we look for H5, the more we will find," said Juan Lubroth, head of infectious diseases, animal services, at the U.N. Food and Agriculture Organization.

Earlier this year, there were several human cases in Britain of H7N2, a strain that also has pandemic potential.

"Europe has already faced many H5N1 challenges in the past. ... What is happening in the U.K. doesn't add anything particularly new to the situation," said Dr. Angus Nicoll, influenza coordinator at the European Centre for Disease Prevention and Control.