Victorian authorities confirmed the rescue mission as defence forces begin relief operations across Australia's southeast.

Two navy vessels had arrived at the coastal town on Thursday, with people to be transferred aboard on Friday morning.

Defence authorities told media on Thursday people could ask to be taken out of Mallacoota, but defence would prioritise who would get to leave first.

Weather would affect where the boats would offload passengers, with the potential for smoke to hamper air rescue efforts.

Bushfires have trapped holiday-makers and locals in isolated towns across the Victorian coast.

Three military helicopters, two ambulance choppers and a cargo plane were on standby in the Gippsland region, at an air base at East Sale.

The HMAS Choules and MV Sycamore, a defence contracted training vessel, left Sydney on Wednesday for Victoria.

While these ships were planned to help rescue operations along the NSW south coast, Prime Minister Scott Morrison said the NSW government had turned down the help after authorities reopened roads in the region.

Tourists and locals were told to leave now before conditions deteriorate again over the weekend.

Fires in southern NSW have claimed seven lives and destroyed at least 382 homes. One life has been lost in the fires in Victoria.

Australian Associated Press