A father and son have died trying to defend their home against the bushfires raging in Australia.

NSW Police Deputy Commissioner Gary Worboy confirmed the two people who died at Cobargo were a father and son trying to defend their home from the Badja Forest Rd fire.

Meanwhile firefighters are warning the thousands of people forced to flee to beaches along the NSW South Coast could potentially be in for a "very uncomfortable and difficult night".

"And we make no apology," RFS Commissioner Shane Fitzsimmons said.

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"The important thing is we wouldn't want to be moving lots of people out by water overnight."

Fitzsimmons said they would look at moving people out tomorrow, working closely with the police.

Dozens of Surf Lifesaving clubs along the coast have opened their facilities to evacuees.

"It is going to be a very long, difficult and dangerous night still ahead."

New South Wales Premier Gladys Berejiklian has confirmed two people have died in bushfires that devastated the village of Cobargo earlier today.

The two men are thought to be dairy farmer Patrick Salway, 29 and his father Robert, 63.

Deputy Commissioner Worboy said: "The two men at Cobargo are residents of Cobargo. A father and son, as we believe. Very tragic set of circumstances. Obviously trying to to their best with the fire as it came through in the early hours of the morning."

He said police were still trying to make their way to a home west of Narooma where a man was also defending his home.

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"Unfortunately we think that the news there will not be good either," he said.

Photos of the main street of Cobargo, which used to be lined by historic, turn-of-the-century buildings, appear to show it completely razed.

There are reports the local school has been destroyed as well as disinfection infrastructure within the Brogo River water supply catchment.

Cobargo, to the west of Bermagui, has been on fire for much of today, with multiple buildings on the main street on fire and RFS crews struggling to save properties.

The town was evacuated earlier today.

The fire affecting Cobargo is the Badja Forest Rd fire near Cooma, which is rapidly moving eastward and was predicted to be among the blazes to expand most significantly, along with a fire in the Snowy Valleys. Almost 100 blazes continue to burn across New South Wales, with dozens uncontained and eight today at "emergency" level.

Meanwhile, a massive fire is set to hit the beach in Mallacoota in the East Gippsland region of Victoria, and locals say the sky has turned black.

The fire has cut power to the town.

"It's not pleasant, it's pitch dark here and the emergency vehicles have disappeared from sight," resident and local community radio presenter Francesca Winterson told ABC Gippsland.

"The power's been out here a long time and we've run out of solar.

"My home's in the fire path, I won't have a home, that's just the way it's going to be, we have to try and be calm."

Victoria's Emergency Management Commissioner Andrew Crisp said firefighters were protecting 4000 people on the town's foreshore this morning.

They have been there throughout the night.

It's understood the plan was if the fire got too close, they'd be surrounded by CFA volunteers and they would create a wall of water to protect them as a last defence.