A case of bird flu has been confirmed at a chicken farm in Saga Prefecture, the agriculture ministry said Saturday, marking the season's first confirmed case of the highly pathogenic avian influenza at a poultry farm in Japan.

The Saga Prefectural Government has started to cull around 40,000 chickens raised at the farm in the city of Kashima. The agriculture ministry asked prefectural governments and poultry farmers across the country to be on high alert.

A genetic test conducted in the early hours of Saturday confirmed the case at the Kashima farm after an increase in the number of dead chickens there was reported Friday afternoon.