Up to 70 homes and buildings destroyed by ferocious fast-moving bushfire

A seaside town on New South Wales' far south coast has been left devastated after a fast- moving bushfire ripped through dozens of homes and businesses.

It's feared up to 70 properties, including a popular caravan park, in Tathra east of Bega were destroyed in the fast-moving blaze that broke out yesterday.

The fire, fanned by very strong winds and high temperatures in the state's east, burned through several kilometres of bushland and crossed a river before it reached the picturesque township.

The NSW Rural Fire Service says the 1000ha blaze is still out of control.

However, the threat level was downgraded after a southerly wind change helped ease hot conditions. No-one has been reported missing so far.

But residents have been traumatised by the speed of the flames which took barely half an hour to cross the Bega River and hit the Tathra area.

"It's horrible but it could have been a lot, lot worse," one resident told Nine Network today.

Bega Valley Mayor Kristy McBain said about 35 properties had been damaged or destroyed and the town's roads, water system and sewage treatment plant were also damaged.

But later that estimate was raised as authorities began to assess the area.

"Our early indications are that the number of buildings impacted is likely to climb above 70, but we will confirm that with the work of the building impact assessment teams this morning," RFS Commissioner Shane Fitzsimmons told Network Seven.

"We have this awful situation throughout the community of Tathra, where we have damaged buildings, damaged homes, and infrastructure," he said.

Communication were affected after a mobile phone tower collapsed, making it difficult to determine how many people remained in the town. "There are no reports of any loss of life, so it will be very much about trying to track these people down," McBain told AAP.

Hundreds of residents and tourists fled to evacuation centres in Bega and Bermagui, after access to Tathra cut off, to spend the night waiting for news.

Tathra Beach Motor Village said it had experienced "significant" damage and would be closed until further notice. The blaze tore through its front office and reception area but management wasn't able to confirm what other parts had been affected.

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"This is a very dire and devastating situation for all involved," a post on the park's Facebook page said.

Tathra Public School, Bega High School, Tanja Public School and Bournda Environmental Education Centre will all be closed. It's unclear if any have been damaged or destroyed.

The Insurance Council of Australia has declared the fire "catastrophe", meaning claims by those affected by the blaze will be given priority.

However, the ICA said it's too early to determine the extent of buildings lost or estimate the financial toll. Temperatures are expected to reach 30C in the Bega region tomorrow, with light easterly winds in the afternoon.

- AAP