Swedish veterinarians have identified a mink with an aggressive form of the H5 bird flu virus and had the mammal put down, the National Veterinary Institute said on Monday.

The animal was found in the Blekinge region of south Sweden, an area where several bird flu cases have been found. What is initially described as an aggressive form of H5 bird flu is often later confirmed as the highly pathogenic H5N1 virus.

The mink probably got the disease from eating wild birds that were already infected, the Institute said in a statement.

The H5N1 bird flu virus can infect humans who come into contact with infected poultry and has killed more than 100 people since late 2003.

The virus has also recently been detected in a marten, a weasel-like mammal, and cats in Germany, and a dog in Azerbaijan.

The World Health Organisation says that so far only domestic poultry are known to have played a role in transmitting the virus from animals to humans, but it has called for further investigation into the significance of infection in other mammals.