Japan has confirmed its fourth outbreak of bird flu since the beginning of the year, the Agriculture Ministry said on Thursday.

More tests are being carried out to check for the presence of the H5N1 strain, it said in a statement.

The latest outbreak hit a farm in the southwestern prefecture of Miyazaki, Japan´s biggest poultry-producing region.

The farm kept about 93,000 birds for their eggs.

With the confirmation of bird flu, all the birds on the farm will be culled, the site will be disinfected and movement of people and goods within a 10-km (6-mile) radius will be restricted.

The ministry said it estimated there are 100 farms raising about 3.5 million birds within the restricted area.

The H5N1 bird flu has already been confirmed at two other farms in Miyazaki prefecture, and one farm in the western prefecture of Okayama.

There have been no reported cases of human infection from the virus in Japan.

The last outbreak of H5N1 in Japan occurred in 2004 when it reported four cases.

The H5N1 virus has killed at least 164 people worldwide since 2003, most of them in Asia, and over 200 million birds have died from it or have been killed to prevent its spread.