The Health, Labor and Welfare Ministry unveiled a plan Monday empowering the government to ban public gatherings and quarantine people to counter the potential outbreak of a new strain of bird flu against which humans have yet to develop an effective defense.

Bird flu has killed more than 60 people in Asia, and it is feared the virus may mutate into a form that can spread easily between humans.

The ministry has estimated that if 25 percent of the population contracts bird flu, the number of deaths in the worst-case scenario would reach some 640,000.