Fire crews in South Australia have spent the night battling an emergency bushfire on Kangaroo Island, which is threatening to engulf most of Australia's third-largest island.

Key points: The CFS is battling an emergency blaze on the western half of Kangaroo Island

The CFS is battling an emergency blaze on the western half of Kangaroo Island The island townships of Vivonne Bay and Parndana have been evacuated

The island townships of Vivonne Bay and Parndana have been evacuated Ferries are running to get people off the island, and last-resort refuges have been set up

On Friday night, Kangaroo Island's Ravine fire was described as "virtually unstoppable" and the Country Fire Service (CFS) has issued bushfire warnings for the entire 4,400-square-kilometre island.

At 3:00am Saturday, a watch and act warning was issued for the western end of the island, which includes areas west of Parndana such as Flinders Case, Vivonne Bay, Kelly Hill, Western River, Hanson Bay, Gosselands, Middle River and Stokes Bay.

People located in these areas are urged to leave now as a scrub fire is burning in various locations in the area.

An advice warning is in also place for properties east of Parndarna in the areas of Menzies, Seddon and Seal Bay, including Kingscote and Penneshaw.

People on the eastern half of the island are urged to remain alert and monitor local conditions.

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Kingscote and Penneshaw, located on the island's east, have been identified as Bushfire Safer Places.

The distance from Flinders Chase National Park, where the fire is burning on the western end of the island, to the main town of Kingscote in the east, is about 85 kilometres.

Kangaroo Island Mayor Michael Pengilly has reported significant property damage to hotels and facilities around Flinders Chase National Park.

Multiple scrub fires continue to burn across Kangaroo Island's western half, such as this one in Cape Torrens. ( Twitter: Glen Bubner )

Up to 150,000 hectares has already been burnt on Kangaroo Island as 150 CFS personnel work to stop the fire's spread.

CFS deputy chief officer Andrew Stark said the fire conditions "prevailed for far longer than we hoped for" and the fire was "moving in a dangerous manner towards the east".

"The ferry service will continue to operate for people to get off the island," he said.

He said the fire was much larger than the 2007 Kangaroo Island blaze, which destroyed 95,000 hectares.

Bushfire plumes pictured near De Mole River, Kangaroo Island around 6:00pm last night. ( Twitter: Glen Bubner )

Tourist attractions ablaze on Kangaroo Island

Mr Michael Pengilly said the island's Visitor Information Centre and Kangaroo Island Wilderness Retreat had been destroyed.

He said the Western KI Caravan Park and Hanson Bay Wildlife Sanctuary had also been significantly impacted.

In a statement, Baillie Lodges, which owns the Southern Ocean Lodge, said the tourist attraction had "sustained significant damage" and all guests and staff were evacuated to Kingscote or Adelaide.

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"A small team of six senior staff members remained on-site to monitor the situation and activate the lodge's fire emergency plan," it said

"While the lodge has sustained structural damage … no injuries have been sustained."

Lodge owners James and Hayley Baillie said initial plans were already at hand to rebuild the award-winning luxury lodge.

"We are absolutely shocked and saddened by today's events," they said.

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Watch Duration: 41 seconds 41 s Kangaroos flee from the fire scene on Kangaroo Island.

The Ravine fire is burning through the Flinders Chase National Park in the island's west and the CFS has said "firefighters are now unable to prevent the fire spreading".

"You are in danger. Act now. Identify where you will seek shelter, preferably in a solid building. Only leave if your path is clear to a safer place," the CFS said.

"Heat from the fire can kill you well before the flames reach you."

Mr Pengilly said the main priority was "people — locals, visitors, firefighters".

"The safety of humanity is the prime responsibility at this stage," he said.

Bushfire plumes seen west of Cape Torrens yesterday afternoon. ( Twitter: Glen Bubner )

"It has been absolutely devastating. It's a natural fire, it all started with lightning — it's Australia, it's summer and it all started with lightning and the north coast looks like it has been hit by a nuclear bomb.

"Flinders Chase is going to come out of this badly. You can't stop this thing at the moment, it's bloody impossible."

The CFS extended the emergency zone for the Ravine fire to include Vivonne Bay at about 6:00pm, as emergency services worked to evacuate the tourist hub. Parndana has also been evacuated.

'Truly horrific conditions' as 'fire twisters' flare

Footage of a so-called "fire twister" has revealed the intensity of the flames on the island.

Local resident Brenton posted video to social media of one of several fire twisters breaking out in the inferno, as well as kangaroos fleeing the flames.

A shed and trailer destroyed by the fire on Kangaroo Island. ( Facebook: Leon Bignell MP )

Kangaroo Island is one of several districts across the state under a total fire ban, with extreme fire danger declared for the island.

A relief centre has been established at the Kingscote Football Club on Centenary Avenue.

Flinders Chase National Park has been closed until further notice, along with several other conservation areas on the island and the mainland.

Kangaroo Island is expecting to host a number of cruise ships in the coming days, anchoring off the coast of Penneshaw.

Mr Stark said a decision would be made on Saturday morning about whether those crews will be allowed to dock.

Smoke fills the sky near Lucindale as fire destroys farmland in South Australia's south-east. ( Facebook: Greg Fisher )

Police charge man with 'masquerading' as fire victim

In the Adelaide Hills, an emergency warning was declared for a fire at Kersbrook late on Friday afternoon but was later downgraded to a watch and act.

In a statement, SA Police said a 59-year-old man was on Friday charged with deception after allegedly "masquerading as a bushfire victim" to receive a benefit.

"His actions have caused a great deal of concern in the Adelaide Hills and police appreciate the information provided by the public which has facilitated his swift arrest," it stated.

He will appear in the Mount Barker Magistrates Court next month.

Earlier this week, a 39-year-old Murray Bridge woman was charged with falsely claiming to be a bushfire victim to "obtain donations to the value of $300" from a local church.

Adelaide hit 42.1 degrees Celsius at 3:20pm on Friday, with even hotter temperatures inland, including 44.8C at Port Augusta, 45.4C at Wudinna and 45.6C at Tarcoola.