A man has died and several homes destroyed in a massive bushfire burning in eastern Victoria.

The man's body was found in a burnt-out car in the Seaton area, where at least one home and as many as five have been destroyed.

The fire has burnt through an area of around 48,000 hectares and will continue to burn and threaten communities for weeks to come, Fire Services Commissioner Craig Lapsley said.

At least four holiday shacks within national park boundaries were also destroyed, Mr Lapsley said.

The fire began in the Baw Baw National Park on Thursday and tripled in size overnight, forcing the early morning evacuation of homes in Seaton, Licola and Heyfield.

Mr Lapsley said the rapid expansion had taken crews by surprise.

"The fire was aggressive, very intense and fast moving through the night hours," he told reporters.

"It's been burning like a grassfire in forest conditions."

Peetika Hobson, who has lived in Seaton for 30 years, said her house had been lost.

"As we were driving back to Heyfield hoping to see if the house was still there, we got a text message from our son that he heard our house had burned down," she told Network Ten.

"It becomes quite sad thinking about what you've missed.

"You'll never go home again to the house where your family grew up."

The fire threatened homes in Seaton, Dawson, Glenmaggie and Heyfield on Friday.

Incident controller Bill Johnstone said the fire could also affect the Macalister River valley and Licola, which has been cut off.

He said the crews were working in a deteriorating environment.

"Given the conditions it's probably as bad as it can get," he told reporters at Heyfield.

Mr Johnstone said between four and five homes in the Seaton area are believed to have been lost.

Mr Lapsley said the fire's size and remote location meant it would be a threat for weeks to come.

"One of the problems is that once it buries itself in the deep-seated bush area, the next northerly day it'll then come out near the communities of Heyfield again and Maffra," he said.

"We're now planning for a two-week campaign fire."

Mr Lapsley said the fire would take significant resources to contain.

"Once we move into the wilderness country we're moving into some very remote, and in particular, deep-seated bush environments, which are difficult for anyone to get into, so we can't put ground crews in," he said.

"It's not a single firefront. It's a number of firefronts and it actually sprays, if that's the right word, embers across hilltops which sees the spread of fire from spot fires."

Mr Lapsley said it was likely that livestock, fencing and farm equipment had been destroyed.

Prime Minister Julia Gillard said she felt for those caught up in the fires.

"I want to say to anyone in that position that this summer the Australian people are thinking of you and will be there to support you," she told Fairfax radio.