Bird flu has killed 690 chickens raised by a household in Son Tinh district since June 12, People newspaper said, noting that Quang Ngai and southern Tra Vinh province are being hit by the disease.

Bird flu outbreaks are cooling down in Vietnam, but still making complicated changes, Vietnam Economic Times newspaper quoted Vietnamese Deputy Minister of Agriculture and Rural Development Bui Ba Bong as saying.

Vietnam should keep on carrying out anti-bird flu activities atboth central and local levels, and intensifying the disease-related research, he said.

Vietnam is probing into over 30 variants of bird flu virus H5N1 taken from affected poultry and wild birds.

Bird flu outbreaks in Vietnam, starting in December 2003, have killed and led to the forced culling of dozens of millions of fowls in the country.