A bird flu prevention zone has been imposed by the government to protect British poultry against a virulent strain of the disease that has hit Europe.

The Department for Environment, Food & Rural Affairs (Defra) announced the measures, which will require chickens, turkeys and ducks to be kept indoors for 30 days or be separated from wild birds.

The order applies to anyone who keeps birds, even if they only consist of a few chickens in their back garden. Farmers are being asked to look for signs of infection and take disinfectant measures.

In France, foie gras producers have had to slaughter thousands of birds being prepared for the Christmas market to prevent the spread of bird flu as the country's agriculture minister raised the risk level of the virus from moderate to high.

It followed an outbreak of a particularly severe form of bird flu, the H5N8 virus, at a duck farm in the south-west of the country, prompting fears it could spread throughout the region. There have also been cases in Sweden and other countries.

The government's chief vet, Nigel Gibbens, said the risk to humans was low and no UK cases had been found.

"We are closely monitoring the situation across Europe and have scaled up surveillance in response to the heightened risk," he said in a statement.