The worst fires are burning in Victoria's east and on the NSW south coast, where eight people have died this week and 28 people are missing.

Holiday-makers and residents have been told to get out before it's too late with temperatures in excess of 40C and strong winds forecast for Saturday.

"People getting to places of safety right now is incredibly important," Prime Minister Scott Morrison told reporters as he toured burnt-out towns on Friday.

"Because in about 24 hours from now, or even less, the situation will be far more dangerous."

A state of emergency has been declared in NSW and evacuation orders issued for much of the state's southeast as the Rural Fire Service warns some towns cannot be defended.

Streams of cars, caravans, trucks and buses clogged the highways as people heed the warnings to leave. Dozens of makeshift campsites are springing up in towns deemed safe by authorities, straining resources despite the military's ongoing relief operation.

For Anthony Ellis, who evacuated his family from Surf Beach near Batemans Bay in NSW, leaving was a no-brainer after a blaze burned too close for comfort on New Year's Eve.

"The smoke behind us just changed," he said. "It was just solid walls of darkness."

The family made for the beach, where they were trapped for the next five hours as the fire roared through nearby towns.

"You couldn't even risk it to move through the suburb to check on other people," Mr Ellis said. "We decided we're not going to risk it twice in one week."

A state of disaster has been declared in Victoria as the navy continues its evacuation of about 1200 trapped tourists and residents from fire-ringed Mallacoota, in East Gippsland.

The town was hit by a massive blaze on Tuesday as 4000 people sheltered on a beach amid apocalyptic scenes that were broadcast across the globe.

Evacuees, many with pets, will travel for about 20 hours to the Mornington Peninsula, where an evacuation centre is likely to be set up.

Premier Daniel Andrews says 28 people remain missing in Victoria, on top of two men confirmed dead, the latest a man found at a property near Genoa, in the state's east.

An eighth person was confirmed dead in NSW on Friday after police found a missing 72-year-old man's body in the town of Belowra, in the state's south.

It's bring's the death toll for the fire season to 17 in NSW after police confirmed the death of a 59-year-old man, who was burned while sheltering from a bushfire in a water tank in November.

In South Australia, where one person has died and dozens of homes have been destroyed this summer, a bushfire on Kangaroo Island has become "virtually unstoppable" after it jumped containment lines. An emergency warning had been declared across the entire island.

Late on Friday, the Country Fire Service also issued an emergency warning for a blaze in the Mount Lofty Ranges.

In Western Australia, a series of out-of-control bushfires on Nullarbor Plain have cut the state's only sealed road to South Australia, causing shortages in some Perth supermarkets and stranding hundreds of truckies and travellers at a remote roadhouse on the Eyre Highway.

A second home has been destroyed in Tasmania by a bushfire police believe was deliberately lit. Hot and windy weather will push the fire danger to very high on the weekend, with a total fire ban declared across much of the island.

The ACT has declared a state of alert as toxic smoke blankets the capital.

Across Australia, 20 people have died and more than 1500 homes have been destroyed in bushfires this season.

Australian Associated Press