Thousands of firefighters have been deployed to tackle the blazes.

The nation endured its hottest-ever day on Tuesday, but that record was smashed again on Wednesday - which saw an average maximum of 41.9C (107.4F).

Tuesday's 40.9C had eclipsed the previous record of 40.3C, set in 2013.

Authorities in New South Wales (NSW) are currently fighting about 100 fires, in a crisis that has lasted months.

Premier Gladys Berejiklian announced a seven-day state of emergency due to forecasts of worsening conditions.

"The biggest concern over the next few days is the unpredictability, with extreme wind conditions [and] extremely hot temperatures," she told reporters on Thursday.

Parts of NSW, of which Sydney is the capital, hit temperatures in the early-40s on Thursday. More intense heat was forecast for the rest of the week.

A state of emergency gives fire authorities additional powers to cope with the crisis. It is the second such declaration in NSW since last month.

Bushfires have been raging in Australia for months, killing six people, destroying hundreds of homes and burning millions of hectares of land. - BBC