The deadly H5N1 strain of avian flu was confirmed at Redgrave Park farm. Now, birds at Stone House Farm, in West Harling, Bridge Farm, in Pulham, Grove Farm, in Botesdale, and Hill Meadow, in Knettishall, which are run by Redgrave Poultry, will be culled as Defra officials believe there could be a contamination risk between the five sites.

Geoffrey Buchanan, operations director of Redgrave Poultry, said: "Defra has announced that all the birds on four further farms in the restricted zone are to be culled as a precautionary measure- there being no confirmed disease on any of these four premises.

"We can confirm that that these farms are also operated by Redgrave Poultry and we fully support Defra taking every step it believes necessary to contain this outbreak.

"There is a direct link between Redgrave Park Farm and these four other farms as they share the same farming staff.

"Each farm is too small for a dedicated staff, so a small team of people runs this cluster of farms.

"Despite bio-security measures when entering and leaving the farms and the fact that there are no results to indicate the presence of avian influenza at these farms, Defra has decided there is the possibility of a direct link.

"While naturally saddened to see so many birds culled, we fully agree that the primary concern has to be the containment of the outbreak."

In total, 22,000 free range turkeys will be culled, in addition to 6,500 birds slaughtered at Redgrave Park.