Arsonists labelled Australia's 'terrorists'

South Australian Premier Mike Rann has labelled arsonists "terrorists" as authorities vow to "throw the book" at anyone found responsible for the deadly bushfires that have devastated Australia.

The Victorian death toll had risen to 76 late on Sunday after emergency crews discovered scores of bodies at townships northwest of Melbourne, ravaged by fire.

Twenty-six fires were burning in Victoria taking lives and property, and another 53 were burning throughout NSW.

Victoria Police Deputy Chief Commissioner Kieran Walshe said it was believed some fires in his state had been deliberately lit, but would not say which ones.

"We have our suspicions in some instances but really we do need to get to the position where we can get our investigators and our forensic scientists into the fire scenes to do a full, thorough investigation, see what evidence can be uncovered which will confirm or deny for us how these fires have originated," he told the Seven Network.

One of Mr Walshe's colleagues earlier on Sunday said arsonists could be charged with murder or manslaughter depending on available evidence.

"These people are terrorists within our nation, they are the enemy within and we have to be increasingly vigilant about them when you consider that 20 percent of the fires in South Australia so far this summer have been deliberately lit," Mr Rann told reporters in Adelaide.

NSW Premier Nathan Rees made his thoughts clear, telling arsonists: "We will throw the book at you".

Federal Opposition Leader Malcolm Turnbull said police should be relentless in their pursuit of arsonists and in bringing offenders to justice.

NSW police have charged a 31-year-old Sydney man with deliberately lighting a fire on the state's central coast.

He faces two charges in relation to a blaze near Gosford which burned 175 hectares of bushland.