Tokyo, Jan 5 : Central Japan on Friday started culling about 50,000 birds after the region confirmed the first highly pathogenic avian influenza outbreak of this season, according to the Ministry of Agriculture, Forestry, and Fisheries of Japan. A highly pathogenic avian influenza outbreak, the sixth reported case in Japan, has been confirmed on a farm housing about 50,000 chickens in the city of Yamagata in Gifu prefecture, after local authorities received reports on Thursday of an increased mortality rate among chickens at the farm, prompting swift action, Xinhua news agency quoted the Ministry as saying. The preventive operation of culling all 50,000 birds on the affected farm started on Friday and is expected to conclude by Saturday, while the transportation of poultry and egg products within a 10 km radius of the outbreak's epicenter from the affected farm to areas outside the designated zone was restricted. Approximately 158,000 birds across 25 poultry farms within this restricted zone will be subject to limitations on movement and transportation. The bird flu season in Japan typically begins in October each year. /IANS