Hugh Williamson in Berlin

An outbreak of bird flu in a poultry farm in Bavaria, southern Germany, was identified on Sunday as the pathogenic strain of the H5N1 virus, the state's environment ministry said.

Vets and farm staff were involved in culling 160,000 ducks and other birds on the farm near Erlangen, north of Munich, in what officials described as the largest such culling action in recent German history.

Experts said the source of the infection had yet to the found, but said the farm had been sealed off, adding that the virus posed no threat to humans. Both the federal government and European Union authorities had been informed, as part of rapid-reaction procedures installed following earlier outbreaks.

A prolonged outbreak of bird flu in early 2006 in north-eastern Germany sparked criticism that politicians reacted too slowly to the disease. On that occasion 250 troops were deployed to help contain the outbreak.