Another case of bird flu has been found at a poultry farm in the Netherlands, the Dutch Economics Ministry reported Sunday.

It is at least the fourth farm in the Netherlands to be affected by the disease in recent weeks. Germany and Britain have also experienced cases of the disease.

All 28,000 birds at the farm in the western municipality of Zoeterwoude were being culled, the ministry said, and a cordon within a radius of 10 km (6.2 miles) the site has been imposed as well as a ban on the transportation of poultry products.

"The birds are infected with the H5 variant of the flu, but it's not yet known whether of the highly pathogenic variety or not," the ministry added in a statement.

Dutch authorities have previously said that while highly infectious between birds, these flu strains can only infect humans who come into direct contact with infected birds.

The news delivers another blow to the agricultural industry in the Netherlands, one of the world's biggest exporters of poultry and eggs.

"The blow is so much harder as we were on the eve of easing the restrictions we implemented in the last two weeks," Eric Hubers, who chairs the poultry arm of the Dutch agricultural organization LTO, said in a statement.

Tests show that the strain of the bird flu virus found in many of the European cases so far is similar to the one that wrought havoc on poultry flocks in South Korea earlier this year, the World Organization for Animal Health (OIE) has said.

South Korea slaughtered millions of farm birds in a bid to prevent the outbreak from spreading.

se/glb (AFP, AP, Reuters, dpa)