The fires have destroyed at least 750 houses, leaving hundreds of people homeless, and some 14,000 residential buildings are without electricity.
Police do not rule out that the death toll could rise further.
The fires have affected more than 220 hectares of land, and 4,000 firefighters in the state of Victoria are working to extinguish the blazes, which are now reaching New South Wales.
Christine Nixon, chief commissioner of Victoria's police, said some of the fires in Melbourne, Australia's second-largest city, were started deliberately. A team of criminal investigators has already begun work.
The weather has been making things worse, with temperatures reaching up to 47 degrees Celsius (116 Fahrenheit) and strong winds helping fires to spread. Australian weathermen predict abnormal heat in Victoria in the next few days.
Bushfires in 1983 killed 75 people and destroyed some 3,000 houses in the states of Victoria and South Australia.
