All were transported to hospital by ambulance with possible spinal and neck injuries.

NSW Deputy Premier John Barilaro said he was briefed on the incident by the NSW Rural Fire Service. He said an investigation was ongoing and he would not speculate on further details.

RFS spokesman Greg Allan confirmed the incident and said three people remained in hospital overnight.

South Coast residents faced a challenging night on Thursday as the Clyde Mountain and Badja Forest fires merged creating a massive front of flame stretching from Bega to Bundanoon.

Properties are reported to have been lost but the RFS would not confirm this until a building impact assessment was undertaken on Friday.

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Gusty winds and hot temperatures pushed the Clyde Mountain fire across Araluen Road on Thursday, causing it to spread quickly towards Moruya.

The NSW Rural Fire Service had warned residents of Moruya, West Moruya, Mogendoura and Wamban to seek shelter as the fire arrived. Residents in areas from Moruya to Tuross Head, and Bumbo, Bodalla and Eurobodalla were told it was too late to leave.

As of Friday morning, residents in those areas were advised to monitor conditions.

The RFS said conditions were expected to ease on Friday as a southerly change brought light rain and cooler conditions to fire grounds across the South Coast.

Bodalla resident Duncan McLaughlin sheltered with his parents in a cellar as the fire front swept through their Bumbo Road acreage shortly after 3pm on Thursday.

They emerged to find their home safe, but outbuildings burning fiercely and their water supply exhausted.

The family feared for their many horses and Mr McLaughlin broke down when the herd was found safe, despite blazing creek flats and paddocks.

The fire continued to push towards the coast, with Turlinjah and Tuross Head residents on alert.

The fires have closed the Princes Highway between Cobargo and Bermagui Road and between Hector McWilliam Dr and Wiltshire Lane.

Essential Energy said 7600 properties lost power due to the fire activity, including those in Rosedale, Mossy Point, Broulee, Tomakin, Malua Bay, Moruya, Mogendoura, Cobargo, Bermagui, Wallaga Lake and Beauty Point.

Many residents of Akolele, Wallaga Lake and Coolagolite evacuated to Bermagui to seek shelter.

Further south the Bega evacuation centre was again opened, awaiting anyone requiring aid from the multiple fires burning out of control.

The Currowan fire, burning between Batemans Bay and Kangaroo Valley, was not upgraded from advice on Thursday. Its status is labelled as "being controlled".

Thursday's bushfires were threatening the same areas in southern NSW that were scorched in recent weeks.

"Down through the region it's been very hot, very dry and it's been very windy," RFS Commissioner Shane Fitzsimmons said.

"It was another very difficult, aggressive fire weather day, which resulted in so many of these fires spreading and breaking out."