"Your life is at risk," South Australian Premier Jay Weatherill told residents of the Mount Lofty Ranges east of Adelaide, urging them to leave as the "incredibly dangerous fire" raged in rugged scrub.
"If you've decided to stay, you need to be aware that the fire will become incredibly scary and could lead you to change your mind at some point. It could be a catastrophic decision for you to leave late," he said.
"It's a bit frightening," said Graeme Zucker who left Kersbrook near the blaze and was waiting anxiously to find out whether his home still standing.
"You might be lucky, you might not be," he told Australian Associated Press. "We won't know until the roads are opened and we can drive back and come around the corner. If you see the house there, you jump for joy. If you don't, well you don't jump for joy."
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"There's not a fire service anywhere in this world that could put this fire out at the moment," Ian Tanner from the Country Fire Service told residents who fled their homes.
Residents of 19 towns in the Adelaide Hills, an area with a population of about 40,000 dotted with scenic villages and known for its farming produce and wineries, have been urged to leave amid the worst blaze the area has seen in decades.
So far five homes have been destroyed in the fire and reports have suggested that dozens more could be lost but authorities said this could not be confirmed until they were able to visit the area.
"At the moment, we have a fire which is extremely dangerous and it is burning under extremely adverse conditions," South Australia's Country Fire Service chief Greg Nettleton said.
"Right at this moment, residents in the Adelaide Hills are being confronted by a fire which hasn't been seen in the hills since the 1983 bushfires of Ash Wednesday."
The 1983 disaster killed more than 70 people in South Australia and Victoria and destroyed thousands of homes and buildings.