More than 35,000 chickens died in a bird flu outbreak in southern Russia.
More than half a million other chickens at the farm are to be destroyed to prevent the virus from spreading, said Rostov regional emergency services officer Sergei Kozhemyaka.
In September, authorities reported an H5N1 outbreak at a poultry farm in the southern Krasnodar region. In February, the strain was confirmed in several suburban Moscow districts, where it killed hundreds of domestic birds and forced the slaughter of 2,000 more birds.
No human cases of bird flu have been reported in Russia , which had its first reported cases of H5N1 in Siberia in 2005. World health authorities are tracking the H5N1 strain out of concern that it could mutate into a form more easily transmitted among people, sparking a global flu pandemic.