French authorities have confirmed that the deadly H5N1 strain of bird flu killed three swans in eastern France, in the country's first outbreak of the disease in more than a year.

The Ministry of Agriculture in a statement Thursday, stressed the importance of protecting domestic fowl and poultry in mainland France from the virus and from contact with wild birds.

Agriculture Minister Michel Barnier raised the threat level from the disease from "moderate" to "high" following the test results.

Authorities have sealed off the one-kilometer area around the pond at Assenoncourt in the Moselle region, where the three swans died.

France has stepped up surveillance after a number of birds tested positive for the H5N1 virus in Germany and the Czech Republic last month.

The H5N1 strain can affect humans and has killed at least 191 people since 1993, with most of the deaths in Indonesia.

Some information for this report was provided by AFP, AP and Reuters.