Australian Prime Minister Scott Morrison is defending his government's record on tackling climate change, rejecting claims that it is in any way exacerbating bush fires sweeping the continent.

While he labeled the fires a "national disaster" on Thursday, Morrison told reporters in Melbourne that Australia was "getting results" in its efforts to tackle global warming.

Pressure has been ramping up on Morrison to take more concerted action on the issue after toxic smoke from more than 80 blazes across New South Wales again enveloped Sydney this week, triggering health alerts. The fires have burned 2.7 million hectares of land and destroyed about 700 homes.