Strong winds and temperatures of 34 degrees in south-eastern Australia saw officials ban the lighting of fires outdoors and urge residents to prepare rural properties for "ember attacks," when embers from a fire are carried by winds.
"The sky's very dark, with the sun burning orange through the dark smoke," a resident told national broadcaster ABC as more than 100 mostly volunteer firefighters tried to hold back a blaze at Springwood, in the Blue Mountains 70 kilometres west of Sydney.
In Newcastle, 170 kilometres north of Sydney, a plume of smoke closed the airport.
Residents of Balmoral, 120 kilometres south of Sydney, were urged to pack up and leave after reports of a house being razed and 20 more under threat.
Fire-fighting aircraft were grounded because it was not safe to fly due to high winds and low visibility.
Rural Fire Service spokesman Joel Kursawe told reporters that winds of up to 80 kilometres per hour were capable of carrying burning embers over 6 kilometres.
Rural Fire Service deputy commissioner Rob Rogers tweeted: "Residents please take extreme care. Very serious danger to life today."
Voice of Russia, dpa