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By Christine Chen
Victoria's Emergency Management Commissioner Tim Wiebusch told a news conference that firefighters were battling 30 active blazes, with the state's fire danger rating on Friday at "catastrophic", the highest level.
Authorities said damaging winds and temperatures up to 46 degrees Celsius (114.8 degrees Fahrenheit) forecast for Victoria’s north would mean any fires burning will be "undefendable".
"Today represents one of the most dangerous fire days that this state has experienced in years," said Victoria's state Premier Jacinta Allan.
A blaze near the town of Longwood has burned through more than 35,000 hectares (86,486 acres) of bushland, while a blaze near Walwa has grown to around 20,000 hectares (49,421 acres).
Both started on Wednesday as an intense heatwave in the country’s south produced the worst fire conditions since 2019, when bushfires destroyed large tracts of southeastern Australia, killing 33 people, in what became known as the Black Summer.
The largest fire near Longwood had destroyed community and residential property, including multiple homes, a community centre and a telephone exchange, said Wiebusch.
"We can't confirm those numbers at this stage, it's still too dangerous to get in and on the ground," he said.
Victoria Police Deputy Commissioner Bob Hill said two adults and a child were unaccounted for in Longwood after firefighters told them to shelter in their house on Thursday.
"They alerted those people that the risks are great, the risks are so high that they needed to take shelter, that it was too late for them to leave," he said.
"Later that afternoon, those same fire service representatives reattended that area to see the house they saw those three people standing in front of had been completely destroyed," he said.
The Walwa fire had burned through a pine plantation but had not yet caused any property losses.
Dozens of communities near the fires have been evacuated and many of the state's parks and campgrounds are closed.
(Reporting by Christine Chen in Sydney; Editing by Michael Perry)