The death toll from Australia's deadliest bushfires has reached 200 as police continue to search through ash and rubble of several razed towns in the southern state of Victoria.

Australia has an arson investigation after the fires, fanned by a heatwave and strong winds, swept through towns north of Melbourne on 7 February.

Prime Minister Kevin Rudd has described the fires, with at least one deliberately lit, as ‘mass murder’.

A man has been charged with arson causing death over one of the bushfires, which killed 21 people.

In Victoria, arson carries a jail term of two to 15 years, and 25 years if there is loss of life.

The fires were the worst natural disaster in Australia in 110 years.

The previous worst bushfire was the Ash Wednesday fires of 1983 which killed 75 people.