The deadliest wildfires in Australia's history are now being blamed in the deaths of at least 108 people and the destruction of entire towns.

Searing temperatures and wind blasts created a firestorm that swept across Victoria state, where at least 750 homes were destroyed.

Prime Minister Kevin Rudd calls it "an appalling tragedy for the nation." And he told Nine Network television, that if any of the deadly fires were set, "There are no words to describe it other than mass murder."

Witnesses have said the skies rained ash and trees exploded, as temperatures of up 117 degrees combined with blasting winds to create furnace-like conditions.