Tens of thousands of hens have been killed after bird flu was discovered on two poultry farms in Swifterbant in Flevoland and Bennekom in Gelderland, the agriculture ministry has confirmed.

In total, the two farms were home to 67,000 birds, all of which have been killed in an effort to prevent the virus from spreading.

Some 87 other poultry farms are within a 10-kilometre range of the Bennekom farm, and all transport of eggs and birds in that area has now been banned. There are 16 other poultry farms within 10 kilometres of the Swifterbant farm, where all movement of birds and eggs has also been halted.

Bird flu has been identified at several farms, a pheasant breeder and a petting zoo in recent weeks. On Friday, 120,000 laying hens were killed in Drogeham in Friesland, and last month 161,000 hens in Dodewaard in Gelderland were also slaughtered.

On October 16, the farm ministry ordered that all farmed birds be kept indoors to stop potential exposure to the virus, which is also spread by wild birds. The previous indoor order had ended in July.