Australians have cheered US firefighters walking through Sydney airport to join the battle against bushfires that have killed 26 people.

US officials confirmed 100 firefighters were being dispatched to support 159 already in the country where 2,000 homes have been destroyed and eight million hectares scorched by wildfires.

Footage was shared by New South Wales Rural Fire Service Commissioner Shane Fitzsimmons of the reinforcements who will head to Victoria.

'As they came through the arrival gate, those gathered gave a spontaneous and lengthy round of applause, reflecting the gratitude and admiration we all have for their generosity and assistance,' Fitzsimmons said Thursday.

HEROES: Footage was shared by New South Wales Rural Fire Service Commissioner Shane Fitzsimmons of the reinforcements who will head to Victoria to help battle bushfires that have destroyed 2,000 homes and scorched an area the size of the island of Ireland

A fire burns near Tomerong, New South Wales, yesterday - after it was lit intentionally in an effort to contain a larger fire nearby

US firefighter John Szulc told ABC News: 'I'm not really worried, I think we're well trained ... We've got to learn from your local people in how we can do business and fit in with your system.'

It comes as the US National Interagency Fire Center (NIFC) confirmed 20 seasoned firefighters from Angeles National Forest in LA headed to Australia on Monday.

That group will replace a crew who have been helping in Australia since early December, including crack helicopter teams with vast experience in tracking forest fires and putting them out before they grow.

NIFC spokeswoman Carrie Bilbao told ABC that the firefighters were receiving training on poisonous snakes and insects native to the region before heading out.

'They're there to work with Australia in any capacity needed,' Bilbao said.

US firefighters arriving in Sydney on Thursday. Another 100 firefighters are to be sent to Australia, US officials confirmed Tuesday, to support the 159 already in the country

The NIFC is in charge of US wild firefighting missions but over the winter months personnel can be freed up to help with fires elsewhere.

America, Australia and New Zealand have been involved in such exchanges for over a decade, but the last time US firefighters were sent there was in 2010.

'As the extreme fire danger continues across Australia, the Department of the Interior will continue to do all that we can to support requests for assistance,' said Craig Leff of Interior Department Fire.

It comes as Victoria state premier Daniel Andrews warned residents on Thursday it was 'just the beginning' of the bushfire crisis with a heatwave expected to bring further misery.

A firefighter backs away from flames in Tomerong, New South Wales, yesterday with fire crews scrambling to contain Australia's bushfire crisis

A Rural Fire Service volunteer is given instructions by a colleague as he douses a fire near Kulnura, New South Wales

'We're just at the beginning of what will be a really, really challenging summer,' Andrews said.

Bushfires have flared again with temperatures soaring to 100F on Kangaroo Island in South Australia, 24 hours after soldiers went door-to-door to warn residents to leave the town of Parndana on the island.

By Thursday afternoon, Kangaroo Island was also being threatened by fires that were expected to burn for days to come.

'The conditions are such that it is continuing to present a significant risk to the firefighters who are working hard to control the fires, and to anyone else in the vicinity,' Country Fire Service chief Mark Jones said.

In neighboring Victoria the 'state of disaster' was extended for 48 hours ahead of scorching temperatures that were due to set in Friday, further stoking massive fires.

'It's a very dangerous and dynamic situation that will confront us over the next 12, 24 and 36 hours,' Victoria Emergency Management commissioner Andrew Crisp said.

A wildlife rescuer carrying a koala with burnt hands and feet near Cape Bouda on Kangaroo Island

Scientists say the drought-fuelled blazes are being worsened by climate change, which is increasing the length and intensity of Australia's fire season.

Despite cooler weather and rainfall providing some relief in some bushfire-affected areas this week, almost 150 fires were still burning in worst-hit New South Wales and Victoria.

Vast tracts of the states are facing 'severe' fire danger tomorrow, with some areas expected to experience 'extreme' conditions.

'Don't get complacent with the rain that we've seen,' Victoria police minister Lisa Neville said.

'These fires are absolutely still moving, still growing in our landscape and they pose significant risk to communities.'

Firefighters have been taking advantage of this week's milder weather as they race to contain bushfires ahead of Friday.

They have been clearing vegetation and carrying out controlled burns in an effort to protect areas like the coastal town of Eden, where a large bushfire is burning to the south.

Fire and rescue personnel run to move their truck as a bushfire burns next to a major road on the outskirts of the town of Bilpin, New South Wales

Firefighters have been taking advantage of this week's milder weather as they race to contain bushfires ahead of another heatwave

'It only takes a spark to get a fire burning, and that's our concern for tomorrow,' Rural Fire Service superintendent John Cullen told a local council briefing.

The Rural Fire Service said a helicopter pilot who had been waterbombing a fire in the area ditched his aircraft into a dam Thursday afternoon, managing to free himself and swim to shore.

In some burnt-out areas people have turned to the painful task of rebuilding their homes and lives, with the process expected to take years.

New South Wales announced Thursday it would spend 1.2billion Australian dollars (£630million or $822million) on restoring infrastructure in fire-ravaged areas.

That comes on top of a separate A$2billion (£1billion or $1.4billion) national recovery fund earmarked to help devastated communities.

'We are always standing shoulder-to-shoulder with those who have been impacted by the devastating fires, this catastrophe which has come to New South Wales and we are stepping up to make sure we provide that support,' NSW premier Gladys Berejiklian said.

Workers cut down burnt trees to clear the roads after a bushfire in Batlow, New South Wales

Strike teams perform controlled burning west of Corryong ahead of dangerous conditions later in the week

The bushfire toll has not been limited to human losses - the blazes have also wreaked wide-ranging environmental damage.

University of Sydney scientists estimate one billion animals have been killed in the fires. The figure includes mammals, birds and reptiles, but not frogs, insects or invertebrates.

Bushfire smoke has shrouded Australia's major cities in toxic haze for weeks, causing major public health concerns.

The smoke has also traveled more than 7,400 mile) to Brazil and Argentina, according to weather authorities there.

Australia experienced its driest and hottest year on record in 2019, with its highest average maximum temperature of 107.4F (41.9C) recorded in mid-December.