A highly contagious strain of bird flu that has affected poultry farmers in France and Germany has now spread to Belgium, officials said on Thursday.

The H5N8 avian virus was identified late Wednesday among birds at a home in the Dutch-speaking region of Flanders between the cities of Brussels and Ghent.

"The virus that has hit our neighbours in the past months has now reached Belgium," said Belgian Agriculture Minister Willy Borsus.

"Professional farmers have not been affected, but we must be vigilant," he added.

Belgium in November preventively implemented confinement measures in order to stop an epidemic during the bird migratory season.

Authorities on Thursday expanded them to include private owners of poultry and other birds.

The H5N8 strain can spread quickly in affected farms, often leading to the culling of thousands of birds.

Since October, the strain has been detected in 15 other European countries including Britain, France and Germany.

Hungary has had the highest number of outbreaks in the past three months, with 201 cases reported in farms and four in wild birds.