The Swiss authorities begin testing migratory birds for bird flu this weekend as part of a Europe-wide screening program, the official website Swissinfo reported Friday.

The detection of bird flu in Russia has prompted European nations to step up preventive measures. Millions of wild birds fly over Swiss territory during the autumn migration period and it is feared that some of them could be carriers of the deadly virus.

According to the Swiss Ornithological Institute, most birds arriving in Switzerland come from Scandinavia and the western part of Russia but there are also some migrants from western Siberia.

The aim of the screening program is to take faeces samples from up to 1,000 water birds and songbirds over a three-month period in the Lucerne and Basel regions. No birds will be killed or injured in the screening process.

If any bird samples test positive for bird flu, the authorities will take steps to limit exposure to infection.

The Swiss Federal Veterinary Office said a four-step response program was already in place, with different levels of severity. One of the measures would be to instruct farmers to keep their poultry indoors.

The H5N1 avian flu virus has killed at least 64 people in Asia since late 2003. Public health experts predict millions of deaths worldwide if there is a mass outbreak of bird flu in humans.

H5N1 re-emerged in South Korea in 2003, after an initial outbreak in Hong Kong in 1997 was brought under control. It has now been found in birds in 12 Asian countries as well as Kazakhstan and Russia.