Poultry experts from the European Commission believe the three cases of bird flu at farms in the Netherlands, Germany and Britain are due to migrating birds, news agency ANP says on Monday.

This infectious form of bird flu is more common in Japan and Korea and has probably been spread by infected birds, the experts say. There is no connection between the three farms where bird flu has been identified. In addition, two farms close to the Dutch farm where the disease was found at the weekend have been given a clean bill of health.

The movement of poultry, eggs and bird manure has been halted throughout the Netherlands for 72 hours following the discovery of a highly infectious variant of bird flu at a chicken farm in Hekendorp, south of Utrecht.

The virus is of the type H5N8 which can infect humans who have intensive contact with the birds and give them flu-type symptoms, junior economic affairs minister Sharon Dijksma said in a briefing to MPs on Sunday evening.

The 150,000 battery chickens at the factory farm are being destroyed. The last time the Netherlands was hit by this infectious variant of the disease was in 2003.

The Netherlands exports some six billion eggs a year, ANP says. The virus has also been identified at a duck farm in northern England and a turkey producer in Germany.