The government will do "everything we can" to contain the spread of bird flu, the prime minister said today.
Gordon Brown's reassurance came after three mute swans in Devon were found dead from the highly pathogenic H5N1 strain of avian flu.
Other birds at the Abbotsbury Swannery near Weymouth are now undergoing testing and the Department for Environment, Food and Rural Affairs (Defra) confirmed a wild bird control area and monitoring area are being established.
Speaking to reporters at Downing Street, Mr Brown said: "We have had to deal with this issue before and the important thing is that people know we have placed protection zones around the affected area."
In a statement, acting chief veterinary officer Fred Landeg added: "While this is obviously unwelcome news, we have always said that Britain is at a constant low level of risk of introduction of avian influenza.
"Our message to all bird keepers, particularly those in the area, is that they must be vigilant, report any signs of disease immediately and practice the highest levels of biosecurity."