Two people have died and a national park has been almost totally destroyed on Australia's tourist haven of Kangaroo Island, authorities said Saturday.

File photo of the Kangaroo Island's Flinders Chase National Park in Australia.

Devastating conditions overnight helped flames rip thorough the island's Flinders Chase National Park and threaten more heavily populated areas of the island.

Two people were killed when flames overran their vehicle near the town of Parndana, police said. They have yet to be identified.

Fires began on Kangaroo Island -- which sits off the coast south west of Adelaide -- on December 20 and have now burned over 1,000 square kilometres (386 square miles).

"This has taken out much of the Flinders-Chase National Park" including building infrastructure, said South Australia premier Steven Marshall.

"There will be very significant wildlife losses on the island," he said.

The national park is home to kangaroos, koalas and echidnas. 

Bushfire warnings were in place for more than half the island and four cruise ships that planned to dock have been cancelled.

The fires burned so intensely that the airfield used by aerial waterbombers had to be evacuated.

Temperatures dropped significantly on Saturday and the warm front that fuelled the blazes headed north and east the to the rest of the country. 

"Fire behaviour has greatly abated on the island although the fires continue to burn and are not controlled," said Mark Jones, chief officer for the South Australia Country Fire Service.

"The weather today should give crews the opportunity to start to get on top, although we expect that the fires will burn for some days."