Bushfires are threatening dozens of communities in Victoria's east and north-east, as a wind change sweeping the state intensifies the threat and firefighters pull back from fire fronts to focus on saving lives.

Authorities are using Army helicopters to get people out of the East Gippsland town of Omeo, after bushfire hit the community about 4:00pm.

Resident Brian Hadden said it went "red and black" as the main fire front hit, before helicopter evacuations began.

"Where I am at the Omeo Recreation Reserve, there is about six or seven big choppers, army and police," he told ABC Gippsland.

"I can see lots of wind and hell of a lot of smoke. It's been a hell of a day and a night."

Authorities believe several homes have been destroyed across East Gippsland, where most remote communities have been under threat from bushfires.

Ollie Pearce at the Omeo Ski Hire shop told ABC Gippsland he could see flames in the hills and a wind change was pushing the fire in the town's direction.

"And also a grassfire as well … it's not looking good," he said.

Several communities across Victoria's Alpine region and north-east have also been under threat, as thunderstorms caused by the fires fuel destructive winds.

CFA Gippsland incident controller Andy Gillham said a south-westerly wind change moving across the region "just basically puts different communities under threat".

Night from hell: Victoria's ordeal by fire worsens by the hour_1
Inset: What's left of Mallacoota waits for its ordeal to end beneath an unearthly red sky. Photo: ABC

About 50 firefighters from the United States are preparing to join the battle against the East Gippsland bushfires, which authorities estimate have torn through more than 700,000 hectares of land.

Deputy chief fire officer Beth Roberts said authorities were working to juggle both firefighting and relief as they responded to the "unprecedented" bushfire emergency across East Gippsland.

"While we are absolutely concentrating on response, it is important for us to be looking at immediate relief and recovery," she said.

Late this afternoon, cooler temperatures reached East Gippsland. It dropped to 17 degrees Celsius at Mount Nowa Nowa and 20C at Orbost, a dramatic drop from 40C earlier in the day.

Sandy Beltrame from the Omeo Caravan Park said at least 150 people were sheltering at the local recreation reserve as she and other residents prepared to defend their homes.

"How am I feeling at the moment? I've got my big girl pants on, and my big girl shirt over the top of it and a broad brim hat and lots of hoses ready to go," she said.

Night from hell: Victoria's ordeal by fire worsens by the hour_2
Inset: Fire and nothing but fire on the horizon as a windshift drives the front towards Omeo. Photo: ABC

Authorities had been warning communities across Victoria's declared disaster zone to evacuate the area before today, amid fears the extreme weather would make bushfires unstoppable.

This afternoon, five evacuation notices and more than a dozen emergency warnings were in place in the state's east and north-east.

Mr Gillham said residents at Cann River, who were urged to evacuate this week, were "essentially isolated" as fire moved towards them from the east.

"We have been in there with the Australian Defence Force aircraft and we have also conveyed people out of Cann River but it is essentially an isolated community, the road is completely blocked by fallen trees," he told ABC Gippsland.

ABC Radio Melbourne caller Graham said sky had turned red there, and he and other residents were waiting to fight fires as the area came under ember attack.

"It's been completely blacked out and red again. But all we can see near us is a few flare-ups," he said.

A truck driver was killed in a single-vehicle crash in Dederang, in the Alpine Shire, about 8:40am.

Police said the truck was travelling along the Kiewa Valley Highway and left the road, clipping trees.

Many of those evacuating the area are using the highway, and one lane of traffic is closed after the fatal crash.

Several bushfire-affected communities have already lost power and phone connections and authorities have warned generators in Mallacoota and Omeo are running out of power.

Ausnet said fuel they had hoped would reach the East Gippsland towns had not arrived, and it was estimated the generators had between 12 and 36 hours of power left.