Australian police search for clues in the hunt for possible arsonists.

At least 173 people have been confirmed killed in the Australian bushfires, but officials say the toll will rise.

State Premier John Brumby said: "There are still a large number of people, in excess of 50 ... who the coroner believes are already deceased, but are not yet identified," said Brumby, as quoted by Reuters. "This is going to be a significant number, it will exceed 200 deaths."

About 25 fires were still burning in Victoria on Tuesday, with a dozen towns placed on alert as strong winds flared.

Australian police are looking for clues in the hunt for possible arsonists. Victoria state Police Commissioner Christine Nixon launched the arson investigation, "Operation Phoenix".

The disaster area, more than twice the size of London and encompassing more than 20 towns north of Melbourne, has been declared a crime zone by officials. Police tape flutters around charred houses where bodies have been found.

The fires have increased pressure on Prime Minister Kevin Rudd to take firm action on climate change as scientists blamed global warming for conditions that fueled the disaster.

"This week's tragedy shows that we are now dealing with a changed climate in Australia and it is now apparent to all just how much we stand to lose," Greenpeace campaigner Trish Harrup said in a statement.

Major bushfires are not unusual, however.

"The fire weather experienced on Saturday ... although infrequent, is not unexpected, as on average this extreme fire weather occurs every 5 to 20 years," said Justin Leonard at the Commonwealth Scientific & Industrial Research Organization.

Australia is particularly vulnerable to climate change because of its hot, dry environment, but dependent on coal-fired power, Rudd has set a target to cut overall greenhouse gas emissions by only 5 per cent by 2020.