Yin, Chengjie vice-minister of agriculture, said more cases have been caused by migratory and wild birds.

    "The number of dead migratory and wild birds reaches a record high," he told a press conference.

    Citing analysis by experts, he said the source of the epidemics in China this year is closely connected with the aforementioned birds.

    Yin said the virus found in those birds contain increased virulence of bird flu.

    The virus can not only brings about death to chickens, but also make the water birds such as ducks and geese affected, which was rare in the past, he said.

    He predicted that as the air temperature gets colder, there would be greater risk of bird flu outbreaks.

    Yin said the epidemic also posed growing threat to human being as the first human case of bird flu has been reported on the Chinese mainland.

    Large proportion of household-raised poultry and backward chicken farming methods have made it more difficult for the prevention and control of the epidemic, he said.

    There is a long way to go for China to improve its avian flu prevention and control mechanism at grassroots-level, he said.

    He called for greater efforts to prevent and control the bird flu epidemic and take resolute measures to prevent human infection.

    China has by now confirmed 21 bird flu outbreaks in nine provinces, autonomous regions and municipalities, he told the press.

    The bird flu outbreaks killed 144,624 poultry while a further 21,184,200 were culled, Yin said, warning the H5N1 situation in the country was "severe".

    All poultry within a three-kilometre radius of the affected spots are ordered to be culled, a measure taken by the Chinese government to curb further outbreaks.

    Jia Youlin, chief vet of the ministry, said 60 percent of chickens have been vaccinated.

    He said the vaccines developed by China are capable of containing the virus and preventing it from spreading, including those highly pathogenically avian influenza, if used properly. Enditem