Updated

A bird flu outbreak sickened 2,100 geese in eastern China and killed about a quarter of them — the country's second outbreak reported in a week, a U.N. official said Tuesday.

The Agriculture Ministry confirmed Monday that the birds died of the H5N1 (search) virus near Tianchang, a city in Anhui province, said Noureddin Mona, the China representative for the United Nations' Food and Agriculture Organization.

The ministry did not say where or when the geese were infected, Mona said.

A report to the World Organization for Animal Health (search), posted on the group's Web site, said the outbreak, detected Oct. 20, affected chickens and geese. It did not specify which kind of birds were infected with the virus. It said 140,000 birds had been vaccinated and that quarantines and other precautions were taken.

According to Mona, about 45,000 birds have been culled within a three-mile radius of the site.

"The situation is not only in China but in Asia," he said. "There's no question about its seriousness."

Bird flu has killed at least 61 people and tens of millions of chickens in Asia since surfacing in 2003. Most recently, Russia, Turkey, Britain and Romania have reported the disease in birds.

China has not reported any human infections.

Officials began stepping up preventive measures last week after H5N1 killed 2,600 chickens and ducks in a breeding facility in China's northern region of Inner Mongolia (search), sparking fears that the virus might spread to humans.

Health experts have warned that H5N1 could mutate into a form that can be easily transmitted between humans and cause a global pandemic that could kill millions.

The main cause of human infections is direct contact with poultry in slaughtering, butchering or cooking, or surfaces contaminated by their droppings, health officials say.

There is no evidence that properly cooked chicken or eggs can sicken people.

Such public health threats have been a politically sensitive subject for China's leaders since they were criticized for their slow response to severe acute respiratory syndrome, which first emerged in the country's south in 2002.

SARS (search) killed nearly 800 people worldwide before subsiding in 2003.

Chinese officials have been more aggressive in responding to bird flu outbreaks, though international experts are urging a rapid response and strong preventive measures.