UPDATE: Firefighters are being kept busy in two states tonight with major bushfires burning in South Australia and Tasmania.

In South Australia, more than 100 firefighters and three aerial water bombers are battling an out-of-control bushfire near Port Lincoln.

The South Australian Country Fire Service says the fire, which is threatening lives and homes, is burning at Sleaford Mere, west of Tulka.

It is travelling in a southerly direction towards Fishery Bay and is burning in scrub.

Residents are advised to take shelter when the fire arrives and to protect themselves from the fire's heat.

CFS state coordinator Malim Watts said  the serious fire was being driven by strong northerly winds which are expected to continue.

Mr Watts said he hoped the winds would soon abate, which will help firefighters gain control of the blaze.

Meanwhile, the Tasmanian township of Zeehan, on the island's west coast, is being threatened by a large bushfire.

The Tasmanian Fire Service has sent 13 firefighting trucks to try to contain the 1600-hectare bushfire that is raging near the town's airstrip.

The TFS says Zeehan, with a population of about 1000, is at direct high risk from the fire front.

There might be embers, smoke and ash falling on homes in the town, it said.

The TFS has advised residents to activate their bushfire plan and says it is too late to leave the area.

"If your home is well constructed, prepared and actively defended, it may provide shelter," a TFS spokesman said.

"If you dont have a plan or your plan is to leave - leave now, but only if the path is clear.

"This may include a neighbouring property or other cleared area close by that is not at risk from fire."