Smoke from Australia's bushfire crisis has blanketed the major cities of Sydney and Adelaide.
In Sydney, locals woke on Thursday to smoke which appeared worse than a fire-driven haze that was seen on Tuesday.
Health officials issued warnings as air quality surpassed "hazardous" levels and some residents donned face masks.
Fire conditions classified as "severe" or higher have affected all six states in the past week. Several states have faced "catastrophic" levels of danger.
Since last month, six people have died in massive bushfires which have caused the greatest damage in the eastern states of New South Wales (NSW) and Queensland.
On Thursday, smoke from one of those blazes shrouded Sydney for the second time in three days, obscuring buildings and turning skies grey and orange.
Air pollution levels were worst in the city's centre and northern suburbs, with one reading nearly 10 times higher than the national standard.
"The smoke is expected to continue for several days," warned the NSW Rural Fire Service.
Some people described the air quality as the worst they had experienced.
Well I have never seen Sydney covered in a blanket of smoke on a regular basis. The air quality is poor, so please take care everyone. Our planet is crying out for help.
— Maurizio Vespa (@mauriziovespa) November 20, 2019
End of Twitter post by @mauriziovespa
Health officials reiterated calls for people to stay indoors and reduce physical activity, especially anyone with health conditions. About five million people live in Sydney, the state capital of NSW.
NSW Ambulance said it had received more than 60 calls for help for smoke-related health problems on Tuesday.
Residents in Adelaide, the state capital of South Australia, also woke to heavy smoke blown from a major blaze west of the city.
It was expected to clear later on Thursday but people there were also being urged to stay indoors, reported the Adelaide Advertiser.
'Like a dusty filter on Sydney'
Shaimaa Khalil, BBC News Australia correspondent
I woke up this morning with a sting in my throat and a cough, and immediately regretted leaving the windows open. The smell got me before I clocked the haze outside. It's like someone used a yellowish dusty filter on Sydney.
Many are likening the air quality to Delhi and Beijing. The smoke is coming from the north and is unlikely to clear today, according to forecasters.
On social media some are arguing that there isn't enough information about air quality and what people should do. And then of course there is the inevitable climate change debate and whether people in Australia should get used to a new normal.
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