Exhausted firefighters said they had finally brought Australia's largest "megablaze" under control Monday, as wet weather promised to deliver much-needed respite for countryside ravaged by bushfires.

New South Wales firefighters said they finally had the upper hand in the fight against the vast Gospers Mountain fire on Sydney's northwestern outskirts, which has been burning for almost three months.

There was some good news Monday as firefighters said they had control over a megablaze near Sydney, but many fires are still burning, and the devastation is widespread
There was some good news Monday as firefighters said they had control over a megablaze near Sydney, but many fires are still burning, and the devastation is widespread AFP / SAEED KHAN

Visiting the area on Monday, New South Wales Rural Fire Service commissioner Shane Fitzsimmons said there was a "small area of burning still to complete" but the "containment prognosis looks promising".

The fire seared an area of national park three times the size of Greater London and lit several connected blazes totalling over 800,000 hectares.

As residents and authorities continued to come to grips with the sheer scale of the devastation, the Bureau of Meteorology forecast some firegrounds areas could get up to 50 millimetres (two inches) of rain in the next week, a relief after a prolonged drought.

The toll on wildlife has been catastrophic, with a billion animals killed, according to scientists
The toll on wildlife has been catastrophic, with a billion animals killed, according to scientists AFP / SAEED KHAN

If that forecast bears out, the New South Wales Rural Fire Service said it would be "all of our Christmas, birthday, engagement, anniversary, wedding and graduation presents rolled into one. Fingers crossed."

Dozens of other fires are yet to be controlled.

Rock badboy Alice Cooper will be among the stars playing a benefit gig in Sydney this weekend
Rock badboy Alice Cooper will be among the stars playing a benefit gig in Sydney this weekend APA / GEORG HOCHMUTH

The climate-change-fuelled fires have prompted an international outpouring and donations from around the world to help communities and animal populations.

AFP / Gal ROMA

Australia's unique flora and fauna has taken a catastrophic hit, with an estimated one billion animals killed, and countless trees and shrubs burned away.

The country's environment minister Sussan Ley has warned that in some areas, koalas may have to be reclassified as endangered.

AFPTV / Iain BOYD

The government has earmarked an initial $50 million (US$35 million) to spend on helping with the wildlife recovery.

"This has been an ecological disaster, a disaster that is still unfolding," Treasurer Josh Frydenberg announcing the emergency fund.

This weekend, Sydney will host a charity gig to benefit fire services, the Red Cross and animal welfare organisations.

Headliners include Alice Cooper, Olivia Newton-John and Queen.

The political impact of the bushfires is also coming into sharper relief.

A poll released Monday showed Prime Minister Scott Morrison's approval ratings have nosedived in the face of widespread anger over his handling of the deadly crisis.

The Newspoll survey showed 59 percent of Australian voters are dissatisfied with the conservative leader's performance overall, and only 37 percent were satisfied, an abrupt reversal since his shock election win last May.

Morrison has been criticised heavily for his response to the months-long crisis -- which included going on holiday to Hawaii, making a series of gaffes and misleading statements about his government's actions, and forcing angry victims to shake his hand.

He also repeatedly stated that Australia was doing more than enough to meet its emission reduction targets, prompting a series of large-scale street protests.

Seeing a backlash, Morrison has since deployed the military, launched the largest peacetime call up of reserves, pledged billions of dollars in aid, increased payments to firefighters, and suggested more work may need to be done on emissions.