Canberra: A vast area of Australia's east coast - including Sydney - is bracing itself for one the nation's worst ever bushfire threats.
More than 60 blazes are burning across the state of New South Wales (NSW) ahead of the predicted "catastrophic" conditions on Tuesday, the BBC reported.
Authorities warn that fires will spread quickly amid forecasts of hot temperatures and strong winds.
About six million people live in the region.
People in vulnerable communities have been urged to stay away from bushland, and to flee their homes before the fires escalate. More than 600 schools are closed across the state.
State Premier Gladys Berejiklian, who has declared a seven-day state of emergency, said Tuesday would be "about protecting life, protecting property and ensuring everybody is safe as possible".
Three people have died and almost 200 properties have been destroyed since the fire emergency intensified in NSW and Queensland on Friday.
Authorities said they were facing what could be "the most dangerous bushfire week this nation has ever seen".
Experts have compared the conditions to the 2009 Black Saturday bushfires in Victoria, when 173 people died.
It's the first time that a "catastrophic" level fire warning is in place across the greater Sydney area and in the regions to the city's north and south. The highest level rating was brought in after the 2009 disaster.
Authorities have warned of "extreme, severe and catastrophic" conditions in NSW.
Fire chiefs say they are already battling a front spanning 1,000 km along the north coast of NSW, with several blazes "exceeding 100,000 hectares alone".
A predicted pick-up in wind speeds could cast embers up to 30 km from the main front and cause spot fires, they add.
"Under catastrophic conditions, fires that start and take hold will grow and develop extremely quickly and become large fires very, very easily," NSW Rural Fire Services Commissioner Shane Fitzsimmons said.