The strain, known as H5N1, can be caught by humans and has killed more than 50 people in Asia since 2003. A senior veterinary official told Reuters on Thursday that H5N1 had been found in four villages in north and central Kazakhstan.

Asylbek Kazhmuratov, the ministry's chief vet, told a news conference a fifth village was now under scrutiny.

"In the village of Dubrovnoye in the North Kazakhstan region, 23 of 45 birds kept in a courtyard died," he said. "Preventative measures are now being taken in the village as we suspect bird flu to be the cause." Kazakhstan's bird flu outbreak followed one across the border to the north in Siberian Russia.

Although no humans have yet been affected in Kazakhstan or Russia, there are fears the disease could spread to humans on the Eurasian landmass, possibly unleashing a global influenza pandemic.

The upcoming migration season in September has also created the threat that the virus is spread further afield as birds fly south for the winter.

Kazakhstan's sheer size and small population -- 15 million people in a country the size of Western Europe -- has led Kazakh officials to strike a calm note about the outbreak.

The affected areas are under quarantine and birds inside them are being culled.

But the disease has also continued to advance through Siberia, with mass deaths of wildfowl and poultry registered in three more villages there on Thursday.

Source: Reuters - 12th August 2005