A bushfire is burning uncontrolled in Tasmania's southern wilderness, with authorities issuing a watch and act alert for several townships.
Hobart skies have been covered in smoke from an out-of-control wilderness bushfire that could threaten several tiny townships in the state's southwest.
Tasmania Fire Service (TFS) on Friday morning issued a watch and act alert for Maydena, Tyenna and National Park, warning the Gell River bushfire may put homes at very high risk in the afternoon.
The same warning was at 2.20pm (AEDT) extended to nearby Bushy Park, Ellendale, Westerway and Fentonbury.
The TFS has warned embers from the blaze, burning northwest of the communities, could threaten homes earlier than the main fire.
People have been advised to follow their bushfire survival plans and prepare to leave or defend their homes.
John Youd, who owns Tyenna River Cottage, told AAP the sky above Tyenna was "red and angry" but there was some blue poking through.
"There's a lot of ash, my car is covered in it," he said.
Campers have reportedly been evacuated from Mount Field National Park.
The uncontained fire has already burnt through 8800 hectares of wilderness.
Gordon River Road at Maydena is closed to west-bound traffic.
Smoke from the fire has reached greater Hobart, where a smoke alert is in place.
A Melbourne flight due to land at Hobart International Airport has been diverted to Launceston due to the conditions.
A total fire ban is in place for the eastern half of Tasmania, with the southeast, midlands and Upper Derwent Valley rated an extreme fire risk.
Popular national park tracks at Mt Field, Freycinet and Maria Island have been closed due to the extreme heat.
Friday marks the sixth anniversary of Tasmania's Dunalley bushfires that destroyed hundreds of homes in the state's southeast.
The temperature at Hobart International Airport peaked at 36 degrees but that dropped markedly in the afternoon thanks to a cool change that will move up the east coast.