Bird flu has spread west to a sixth region in Russia, triggering the slaughter of hundreds more birds.
Bird flu has led to a cull of poultry in parts of Siberia
The disease has reached the Chelyabinsk region of the Ural mountains which separate Asia from Europe.
The region is a major industrial centre, whereas the other affected areas - Altai, Novosibirsk, Omsk, Tyumen and Kurgan - are mainly rural.
It is not yet clear whether the latest cases were caused by the strain which can be dangerous to humans.
A quarantine has been imposed in several villages in the Oktyabrsky district of Chelyabinsk - a rural district with hundreds of lakes.
The strain found in the Altai, Novosibirsk and Omsk regions has been identified as H5N1 - the type that has killed at least 57 people in South-East Asia since 2003.
An outbreak of bird flu has also been reported in neighbouring Kazakhstan.
'No human cases'
Russian doctors suspect that migratory birds brought the virus to Siberia.
The emergency situations ministry told RIA Novosti news agency that 10,896 wild and domestic birds had died from the disease so far.
But the ministry said there had been "no cases of sickness among the human population".
There are fears of a global pandemic stemming from the H5N1 type, if it mutates into a form which could spread easily from human to human.
Most of those who have died in Asia are believed to have contracted the virus directly from birds.