Russia's agriculture ministry said that the deadly bird flu virus had been found in a third Siberian province as officials began a mass cull to contain its spread and three ex-Soviet countries imposed poultry import restrictions, the AFP news agency reported.

In a written statement the ministry said the virus had been found in the west Siberian province of Tyumen, following an earlier announcement of outbreaks in the Novosibirsk and Altai provinces.

Novosibirsk's governor, Viktor Gergert, said on national television that the slaughter had begun of some 65,000 birds in the affected areas of Novosibirsk, adding that farmers would receive compensation.

Russian officials confirmed on 29 July that bird flu found in Novosibirsk was of the H5N1 sub-type that can be transmitted to humans and has killed at least 60 people in parts of Southeast Asia since 2003.

The virus appears to have been carried to Russia by birds migrating from Southeast Asia, the agricultural ministry's statement said.

"All the afflicted villages have been put under quarantine and all measures needed to contain the infection are being taken," the statement said. "Checks are continuing concerning information from other areas of the Russian Federation where bird deaths have been noted.".

In response to the outbreaks, several countries in the former Soviet bloc imposed full or partial bans on poultry imports from Russia.

Kyrgyzstan's agriculture ministry said it was banning all poultry imports from Russia, while Ukraine's state veterinary department said it was banning poultry imports from Novosibirsk.

Georgia's veterinary inspectorate said it was banning poultry imports from Novosibirsk as well as Kazakhstan, which has already carried out a cull after bird flu was found at a farm close to the Siberian border.

Health experts have said the westward spread of bird flu to Russia was predictable, following outbreaks in neighbouring areas of western China.