Fourteen people are dead and at least 100 homes have been destroyed as fires burn over tens of thousands of hectares in Victoria and New South Wales.

Six have been killed at Kinglake, four at Wandong, three at Strathewen and one at Clonbinane. Police fear up to 40 people may have died.

Victorian Deputy Police Commissioner Kieran Walshe says he expects the toll to rise.

"Based on the fact we're only just getting into areas, these have been very significant fires, our concern is that it can get worse," he said.

Police say they will strive to confirm the identity of the people killed by the morning.

Victoria is bearing the brunt of the inferno with eleven major fire fronts.

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Kinglake and Healesville, north of Melbourne, are the areas of most concern for authorities, and they say there are between 100 and 150 people sheltering in the Country Fire Authority (CFA) station in Kinglake.

A man is in a critical condition after being burnt over half of his body when he attempted to move a friend's stock away from the fire in the Coleraine area, in Victoria's east, while he was wearing only shorts and thongs.

Another man was taken to Melbourne's Alfred Hospital with burns to the face, and there are unconfirmed reports of another man who was burnt.

Ambulance authorities say there is a power problem at a hospital in Beechworth in the state's north, which may need to be evacuated.

There are emergency medical centres in Coldstream and Whittlesea showgrounds.

It is unclear how many animals have been killed by the fires, but ABC Local Radio in Victoria has fielded a number of calls from people who say their stock and pets have been lost.

CFA chief officer Russell Rees says Victorians need to prepared for the fire threat to increase through the night.

"We have to make a plea to people to realise that just because the southerly wind change has come and the temperature drops, the risk is not gone," he said.

"We've got three or four hours of very significant push in this wind change at least, and we all know from past history that fire at night is even more scary than than fire in the day."

Victorian Premier John Brumby says he has been putting his own bushfire preparations into place at his farm, and he has thanked fire fighters for their efforts.

"Today Victoria has experienced the worst fire conditions in history, even worse than Ash Wednesday of 1983," Mr Brumby said in a statement.

Stretched to breaking point

Fire authorities say new blazes are putting "enormous pressure" on their resources, with all available trucks and more than 3,000 firefighters already committed to fighting bushfires that have been burning through the day.

Temperatures have dropped across Victoria, but there will be little relief, with high winds expected to change direction and force fires onto new fronts.

A fire burning from Kilmore to Yarra Glen, north of Melbourne has turned into a massive blaze of around 10,000 hectares that officials say is almost impossible to control. About 50 homes in Bendigo's west have burnt down and properties in Narre Warren, Narbethong, Coleraine and Labertouch have been lost.

It is believed a primary school in Wandong has also been destroyed.

There are 101 firefighters battling the fire, which has destroyed dozens of homes and buildings and is threatening others at Wandong, Heathcote and Upper Plenty north of Melbourne.

The fire, which has burnt through 4,000 hectares, started east of Kilmore and is moving in a southerly direction between Kilmore East and Whittlesea.

A relief centre has been established at the multi-purpose centre in Bentinck Street in Wallan.

ABC Local Radio received a phone call from Peter Mitchell in Kinglake north of Melbourne, who said the entire town was engulfed in flames.

His situation showed how stretched the CFA's resources were, with no fire trucks present after they had been called to the dozens of fires elsewhere in the state. Mr Mitchell said there was one water tanker in the town.

Gippsland fires

The fires have also destroyed several properties across Gippsland in eastern Victoria.

Thick smoke and ash is blowing across west and central Gippsland and the Latrobe Valley, from fires burning near Drouin, Walhalla, and the Strzelecki Ranges.

The fire on the eastern fringe of the Strzelecki Ranges is currently heading towards Willung South, Carrajung South and Carrajung Lower, and the CFA is warning residents may be directly impacted by the fire.

Earlier, the fire passed through Callignee. Other areas including Traralgon South, Gormandale and Yarram are on alert for falling embers. That blaze is still threatening a number of townships, including Nilma North, Darnum, Neerim South and Noojee, and spot fires have broken out in Warragul.

And a fire burning north of Traralgon is burning in a south-easterly direction, and residents in Toongabbie, Glengarry and Cowwar are also on alert. Earlier it ripped through 600 hectares of pine forests in one hour.

Ricky, from Calignee, south of Traralgon, says her neighbours' houses were destroyed.

She says her husband has been burnt in the blaze, which destroyed the family's cars and a shed, but spared the house.

"The roar from over the hill, I just got too scared, and we went back down towards the house, and ended up getting in the house and the windows cracked," she said.

The Princes Highway has been closed either side of Warragul, in West Gippsland and the South Gippsland Highway is now closed, south of Longford.

There are concerns the fire might damage the coal-fired power station at Loy Yang, but at this stage the fire is threatening neither the station nor the nearby coal mines.

The fire has damaged the ABC's FM transmitter in the region, but ABC Gippsland is still broadcasting emergency information on 828 AM.

It has also been confirmed houses have been lost in a fire around the Bunyip State Park, east of Melbourne, but it is unclear how many. The fire broke containment lines overnight and if the wind changes this evening the fire front may grow in size to 20 kilometres, authorities say.

Electricity supplies

Electricity operators say they are no longer concerned about bushfires affecting supplies in Victoria tonight.

Earlier, supply to 100,000 Victorians was threatened by fires burning near stations in the Latrobe Valley.

But NEMMCO, the company that operates Australia's electricity grid, says the system in that area is now secure and no outages are expected.

Enormous scale

Fires are becoming so big that they are creating their own weather.

Senior weather forecaster, Terry Ryan, says thunderstorms are forming over fire-affected parts of west Gippsland.

"We call it pyrocumulus, where all the ash coming out of the fire causes lifting and convection, and can cause a thunderstorm-looking top," he said.

"You can get thunderstorms and lightning coming out of the top of the fire basically, and that can add to the fire's effect, a bit of a nasty feedback effect that can occasionally happen."

Easing temperatures and winds have reduced the threat posed by a fire at Horsham, in western Victoria, that destroyed five homes, a fire truck and the Horsham Golf Club.

The blaze has burned about 3,000 hectares around the city's outskirts.

The golf club's manager, Jason Maybery, says the damage to the course is extensive.

"Total devastation. The clubhouse and the pro-shop have been gutted," he said.

"The sheds in the middle of the course, it's all been burnt as well and a lot of the trees around our lovely course have also been totally burnt down."

Residents of the Yarra Valley have been told to immediately activate their bush fire plans.

In the north-east, a fire is burning south of Beechworth and is moving in a south-easterly direction.

A blaze is burning in west Bendigo where several homes are believed to have been lost and the Redesdale fire to the south-east of Bendigo has burnt about 6,000 hectares.

Concerned Australians are being urged to show restraint in using the emergency services websites, with several struggling to cope with the increased traffic.

However a CFA spokesman said those concerned about the wellbeing of loved ones should not hesitate to use the sites.

For information on the Victorian fires call the Country Fire Authority's information line on 1800 240 667.

New South Wales

Firefighters in New South Wales are working to establish containment lines around a fire that is threatening homes at Peats Ridge on the state's central coast.

NSW Police have released without charge a 31-year-old man arrested on the Pacific Highway this afternoon on suspicion of lighting a fire on the central coast.

The Rural Fire Service has applauded residents in the area, saying they have worked hard to protect their homes from the threat of embers.

It is one of about 40 fires burning across the state tonight.

The New South Wales Rural Fire Service information hotline is 1800 679 737.