Two people were found dead in a burnt-out car on Monday in southwestern Victoria, where the biggest fire is raging.

Fire officials said it was unclear whether they were killed by the bushfire or died when their car crashed in thick smoke from the blaze.

Three homes and several other buildings were lost at Anakie, 150 km (90 miles) southwest of the Victorian state capital, Melbourne, while farmers estimated that tens of thousands of sheep and cattle had been lost in the bushfires.

Firefighters across all four states were hoping to take advantage on Monday of a respite from the weekend heatwave, when temperatures soared above 40 Celsius (104 Fahrenheit), but the sweltering heat is forecast to return later in the week.

"We're hoping to consolidate (the fires) and certainly the perimeter edges of those fires before the temperatures peak back into the 40s later in the week," Victorian Country Fire Authority deputy chief officer Graham Fountain told Australian television.

"But nothing is guaranteed so we need to remain vigilant."

Earlier this month several homes north of Sydney in New South Wales state and in western Victoria were destroyed by bushfires.

Australia is scarred by bushfires every summer and every few years bushfires blaze into major cities which have fingers of bushland weaving through suburbs.

In January 2004, the deadliest bushfires in 22 years killed nine people and injured dozens in South Australia. The blazes were the worst since Ash Wednesday bushfires claimed 75 lives in South Australia and Victoria in 1983.

In 2003, bushfires destroyed a slice of Australia three times the size of Britain, fuelled by one of the worst droughts in a century. Four people were killed and 530 homes destroyed when fire swept through the capital, Canberra, that year.