The H5N1 strain of bird flu is behind the outbreak in Chelyabinsk, a city in the Ural mountains, the Emergencies Ministry said in a statement on Tuesday.

It said no cases among humans have been confirmed in Russia. "Measures are being taken to prevent the spreading of the infection among domestic birds and to exclude the possibility of the infection moving to humans," the statement added.

Russia is battling to contain a bird flu outbreak, which top health officials say has killed more than 11,000 birds countrywide and could spread westwards to Europe, the Middle East and Africa.

The outbreak was discovered in mid-July in Novosibirsk and has spread through Tyumen, Omsk, Kurgan, Altai and now Chelyabinsk, which is about 1000km from Novosibirsk.

Migrating birds

Senior agricultural officials believe the flu was brought by migrating birds from Asia, where more than 50 people have died from the deadly H5N1 strain since 2003.

"There are about 800 different species of birds in Russia and so there are many different migration flows"

Pavel Tomkovich,
ornithologist

Officials fear that the virus could spread to Europe and Africa as tens of millions of birds continue their migration to warmer climates from next month ahead of Russia's harsh winter.

Chelyabinsk is in the Ural mountains, the geographic divide between Asia and Europe. Russia's top state epidemiologist, Gennady Onishchenko, says migratory birds move on to warmer areas in southern Russia, Africa and Europe in the autumn after nesting in Siberia.

But the diversity of Siberia's bird species makes plotting the flight paths of the birds difficult, specialists in Moscow said.

"There are about 800 different species of birds in Russia and so there are many different migration flows, which criss-cross Russian territory," said Pavel Tomkovich, a senior ornithologist at Moscow's Zoological Museum.

Warmer climes

He said water fowl would leave to winter in warmer climates, flying through Russia's southern regions, northern Kazakhstan, the Caspian and Black seas towards the Mediterranean and north Africa.

Health officials are meeting in
Moscow on Tuesday

That could take infected birds through Russia's agricultural heartland in the south.

Health officials were meeting in Moscow on Tuesday to discuss the situation, the state's consumer watchdog said.

In parts of Chelyabinsk, barriers were placed on roads and local officials imposed a ban on the sale of all poultry products, the Itar-Tass news agency reported.

Farmers are being compensated for birds that were being destroyed, the agency said.

Bird flu comes in different stains, such as H5 and H7, which have nine different subtypes. The H5N1 subtype is highly pathogenic and can be passed from birds to humans, though there have been no cases of human to human transmission.