Scott Morrison says defence personnel stand ready to assist firefighters battle the bushfires raging in New South Wales and Queensland.

But addressing reporters outside Kirribilli House in Sydney, the prime minister also issued a sombre warning.

"Sadly, we have lost two Australians and I fear that we will lose more before the day is out," Mr Morrison said.

Prime Minister Scott Morrison speaks to the media about the federal government's response to the bushfires across NSW and Queensland at Kirribilli House on Saturday. Credit:Dominic Lorrimer

Two people have died and seven people are missing as fires in NSW destroyed at least 100 homes amid warnings of worse to come, while thousands of evacuated residents in Noosa, Queensland are waiting to hear whether their homes are safe to go back to.