Sydney, Australia's most populated city, is being choked by a thick blanket of smoke from nearby brushfires.At least six people have died since the fires started, and more than 420 homes have been destroyed in the past two weeks alone.Pictures of the city show Sydney's most iconic areas appear completely gray.Australia's most populated city was covered with a thick blanket of smoke on Tuesday as bushfires in nearby regions continue to cause devastating damage to Australian communities and wildlife.A series of major wildfires have hit Australia's eastern coastal states of New South Wales and Queensland. As of 4 p.m. local time on Tuesday, there were several major bushfires burning in New South Wales, the nearest one in Gosper's Mountain located some 200 kilometers (125 miles) from Sydney.According to the New South Wales air quality control index, areas in Sydney's north-west and east reported "hazardous" levels of pollutants in the air. The government warned that conditions would be "unhealthy for sensitive people, and could cause symptoms, especially in people with heartor lungdisease."The heavy smoke made Sydney the 12th worst city in the world for air quality, behind global hubs with notoriously bad air quality like Delhi, Mumbai, and Mongolia's capital of Ulaanbaatar.According to the Australian Government Bureau of Meteorology, in addition to the smokey haze, Sydney was also experiencing a heatwave with temperatures soaring to 34 degrees Celsius (93 degrees Fahrenheit).Sydney is home to around 5 million people, equal to roughly one-fifth of the country's population of 25 million.Here are 13 pictures that show Sydney under siege as fires continue to rage in the distance.The entire Sydney skyline was clouded by smoke on Tuesday.New South Wales remains under severe or very high fire danger warnings.In Sydney's Central area, tall skyscrapers were barely visible in the distance.The iconic Sydney Opera House and Sydney Harbor Bridge were heavily obstructed from view.The sprawling city skyline was dark and gloomy.Major tourists sites were completely gray.More than 420 homes have been destroyed in the past two weeks alone.Source: The GuardianThe New South Wales Rural Fire Service warned that the smoke is "likely to hang around for the next few days."Source: The GuardianScientists have said that Australia's fire season is beginning earlier and becoming more extreme as a result of climate change.Still, Australian officials have been quiet on the links between climate change and bushfires that are intensifying as Australia approaches summer.Source: The GuardianSmoke could be seen from planes flying in from interstate.Tweet Embed: //twitter.com/mims/statuses/1196583522875494400'ref_src=twsrc%5Etfw Flying to Adelaide from Sydney the white is not clouds, but smoke from the enormous bushfire front pic.twitter.com/cDQjIa3XoVSome social media users were surprised that a fire 200 kilometers away caused so much smoke.Tweet Embed: //twitter.com/mims/statuses/1196570481425440768'ref_src=twsrc%5Etfw This is the smoke over Sydney this morning. I drove over the Harbour Bridge to work and you could barely see from one side to the other. This is from a fire 200+km away. It's not even summer. #NSWBushfires #ClimateEmergency pic.twitter.com/ME0yTQsomrSix people have been killed by the bushfires which officials called "unprecedented."Tweet Embed: //twitter.com/mims/statuses/1196543493717422080'ref_src=twsrc%5Etfw View from above of the smoke across Sydney on Tuesday morning #bushfires pic.twitter.com/0O8JHDcT87Source: BBC Click here to read full news..