Smoke shrouds the Sydney Harbour Bridge in Australia's most populous city on Thursday. Photo: Cassie Trotter/Getty Images

Smoke from Australia's deadly wildfires blanketed the state capitals of Sydney and Adelaide as air quality exceeded "hazardous" levels on Thursday, the BBC reports.

Why it matters: Thousands of people have fled the fires. Per, much of the country is on high fire alert, as blazes rage across all six of Australia's states. Six people have died in the bushfires in the eastern states of Queensland and New South Wales.

Residents defend a property from a bushfire at Hillsville near Taree, north of Sydney. Photo: Peter Parks/AFP via Getty Images
A NSW Rural Fire Service firefighter mops up after a bushfire in the suburb of Llandilo in Sydney. Photo: Sam Mooy/Getty Images
Trees are burned black after a bushfire in Old Bar, north of Sydney. Photo: Peter Parks/AFP via Getty Images
Firefighters tackle a wildfire that's threatening a home in Taree, north of Sydney. Photo: Peter Parks/AFP via Getty Images
Fire burns near the small town of Deepwater, near Glen Innes in northern New South Wales. Photo: Brook Mitchell/Getty Images
A dehydrated and injured Koala receives treatment at the Port Macquarie Koala Hospital in Port Macquarie, Nov. 2. Photo: Saeed Khan/AFP via Getty Images
Wildfires burn in the distance as children play on a beach in Forster, north of Sydney, Nov. 9. Photo: Peter Parks/AFP via Getty Images
Australian Prime Minister Scott Morrison comforts 85-year-old Owen Whalan at an evacuation center in Taree, Nov. 10. Photo: Peter Parks/AFP via Getty Images
An aerial photo of the fires over northeastern New South Wales, Nov. 9. Photo: Tom Bannigan/AFP via Getty Images
The remains of a house destroyed by fire in Old Bar, north of Sydney, Nov. 10. Photo: Peter Parks/AFP via Getty Images
A fire rages in Bobin, north of Sydney, Nov. 9. Photo: Peter Parks/AFP via Getty Images

Editor's note: This article has been updated with new details throughout.

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