Soldiers of the German armed forces Bundeswehr in protection suits carry plastic bags with the remains of dead birds found on a field near the village of Waase at the Baltic island of Ruegen February 21, 2006. (Photo Source: Xinhua/Reuters)

A dead cat found in Germany was infected with a form of the H5N1 bird flu virus, officials said on Tuesday, the first time the virus has been identified in an animal other than a bird in central Europe.

Health officials urged cat owners to keep pets indoors after the dead cat was discovered over the weekend on the Baltic Sea island of Ruegen off Germany's northern coast, where most of the more than 100 wild birds infected by the H5N1 strain have been found.

The cat is believed to have eaten an infected bird, said Thomas Mettenleiter, head of Germany's Friedrich Loeffler Institute.

Germany's Federal Research Institute for Animal Health said it was still conducting tests to see whether the virus was the deadly strain of H5N1.

The finding may increase concern that the virus could spread to other species in Europe as it has in a number of cases in other parts of the world.

There had so far been no known case of a human becoming infected by a cat.

The WHO said the case of the dead cat in Germany had not raised its concern about the threat to human health.

"We know cats can be infected. We know H5N1 is capable of infecting a wide diversity of mammals. We are not exactly sure what it means for human health, but I don't think it raises WHO concerns," spokeswoman Maria Cheng said.

The H5N1 virus has been detected in around 20 new countries over the past month alone, crossing into Europe and Africa. The virus is endemic in birds across parts of Asia.