Nearly 35,000 birds have died from bird flu since late November at a poultry farm in southern Russia's Rostov region, the emergencies ministry said.
Marina Abramchenko said the birds started dying from Nov 29 from the lethal H5N1 virus at the farm, which holds some 500,000 birds, adding that quarantine restrictions have been introduced in the area.
"We have received the preliminary results of analysis," Abramchenko said, adding that the results showed traces of the H5N1 virus.
Although cases of human-to-human transmission of avian influenza have not been reported, scientists fear the virus could mutate into a strain that could pass easily from person to person, and as a result could cause a global pandemic.
According to a World Health Organisation report on confirmed cases of avian influenza (H5N1), Indonesia is the worst hit country, with 91 deaths registered since 2005. A total of 207 deaths have been registered worldwide since 2003.
In 1918, a pandemic killed over 20 million people worldwide, and health experts fear another pandemic could be imminent.