About 50 people had been evacuated, said ABC radio.
What are expected to be record-breaking temperatures will be accompanied by strong winds and low humidity, creating perilous bushfire conditions, particularly today, which is forecast to be one of the hottest. In Victoria, there is plenty of fuel on the ground, thanks to above average rainfall in recent months.
"Those factors taken together, certainly it is a troubling time," the acting premier, Peter Ryan, told ABC radio yesterday. "Right through the regions we are facing extreme or severe fire conditions." He said thousands of firefighters were on standby.
As locals and tourists in fire-threatened areas were urged to prepare for the worst, forecasters said the heatwave could be the largest and longest experienced in Australia. "This is something that we don't think we've seen before," John Nairn from the Bureau of Meteorology (BOM) told The Australian.
In Victoria, police are targeting known and potential arsonists via a state-wide network of 150 specialist officers which was established in November. "We're really focusing on identifying high-risk individuals," said Assistant Commissioner Steve Fontana.
The federal Attorney-General and Minister for Emergency Management, Nicola Roxon, warned people to keep up with the latest alerts - which this fire season, for the first time, will be sent as texts to the mobiles of Telstra customers in danger areas. Optus and Vodafone will offer the service later this year.
"The next week is set to be a scorcher so it's crucial Australians are prepared in the event disaster strikes," Roxon said in a statement.
"It's crucial that people are aware of fire bans and warnings in their local area ... Up-to-date information is critical when disaster strikes."
In South Australia, grassfires were burning yesterday on Kangaroo Island, in the Clare Valley and in the Adelaide Hills. Firefighters warned that the town of Clare could be threatened if the fire - which is in steep and heavily wooded terrain, making it difficult to extinguish - escaped containment lines when the wind changes direction today.
The state's Outback has already experienced searing temperatures, with 42C recorded in Ceduna and 44C in Nullarbor. The town of Tarcoola is forecast to be the hottest place in Australia, reaching 47C on Monday.
Burning up
Victoria: About 8000 firefighters on alert. Police say they will target known and potential arsonists. Temperatures forecast to reach 40C across northern areas with wind. Melbourne to hit 41C today.
Tasmania: A bushfire was last night burning near Richmond. Temperatures forecast in the high 30s. Hobart tipped to reach 38C, with strong winds.
South Australia: Adelaide to swelter in 42C heat, fire services on high alert. Tarcoola in the north-west to reach 46C. Adelaide's Central Bus Station will stay open around the clock to offer people a place to cool down.