Bushfires in eastern Australia have killed at least three people and forced thousands from their homes, with the death toll expected to rise as firefighters struggle towards hard-to-reach communities.

In the normally picturesque coastal town of Forster - one among dozens hit along the eastern seaboard - vast plumes of smoke shot out from multiple blazes as water bombers swooped in overhead.

Prime Minister Scott Morrison said that, if needed, the military could be called on to help around 1,300 firefighters who are tackling around 100 separate blazes.

Several people are still unaccounted for and 30 more have been injured - mostly firefighters working for hours on end in smoky scrubland and blazing forests of eucalyptus.

"My only thoughts today are with those who have lost their lives and their families," Mr Morrison said, as hundreds of civilians also volunteered to help their hard-hit neighbours.

A body was found in a burnt-out building near the east-coast town of Taree, police said, while another victim was found in a car and a woman died despite medics trying for several hours to save her.

As hot and windy weather eased slightly, the number of most serious fires fell to just a handful from an unprecedented 17 yesterday.

But within an area spanning almost 1,000km, schools were burned and at least 150 homes were destroyed while authorities were forced to evacuate detention centres and old people's homes.

It was a narrow escape for Don Russell, with the fire coming within metres of his home in Taree.

"They've done a top job, them fellas," Mr Russell said after a crew of six firefighters brought the blaze under control.

His next-door neighbours were not so lucky, however - their home went up in flames. No one was home.

New South Wales's rural fire service said an emergency warning was in place for four fires among the dozens raging across the state.

"We're experiencing tinderbox-like conditions across much of the state and all it takes is one spark to start a fire that may burn for days," said Queensland's acting fire commissioner Mike Wassing.

Queensland declared a "fire emergency" and banned the lighting of all outdoor fires.

Meanwhile New South Wales premier Gladys Berejiklian warned that next week's weather forecast "could mean we're not through the worst of it".

Mr Morrison, whose government has played down the threat of climate change, sought to deflect questions about what impact it may have had.

"Australia has been battling ferocious fires for as long as Australia has been a nation, and well before. And we will continue to do so," he said.

Firefighters described the conditions as "difficult" and "dangerous".

In some areas, residents were stuck and told to simply "seek shelter as it is too late to leave".

Local radio stopped normal programming and provided instructions about how to try to survive fires if trapped at home or in a vehicle.

Authorities said some of the fires were creating their own weather conditions - pyrocumulus clouds that enveloped entire towns.

Despite easing conditions, a prolonged drought and high aridity levels will continue to make circumstances combustible.

Earlier this month, some of the same fires cloaked Sydney in hazardous smoke for days.

Today it was Brisbane's turn, with the fires enveloping the city centre in a veil of acrid fog.

Swathes of Australia have gone months without adequate rainfall, forcing farmers to truck in water, sell off livestock or leave their land to lie fallow.

Jim McLennan of La Trobe University said the bushfires were "unprecedented", coming so early in the season and in areas that usually have moist soils and vegetation.

"However, the fire situation is consistent with our new world of bushfire threat associated with climate change," he said.