Australia's prime minister called up about 3,000 reservists on Saturday as the threat of wildfires escalated in at least three states, while strong winds and high temperatures were forecast to bring flames to populated areas including the suburbs of Sydney.

Prime Minister Scott Morrison said 23 people had died in the wildfires so far this summer, including two in a blaze on a highway on Kangaroo Island off the coast of South Australia state, the latest fatalities.

"We are facing another extremely difficult next 24 hours," Morrison said at a televised news conference. "In recent times, particularly over the course of the balance of this week, we have seen this disaster escalate to an entirely new level."

He also confirmed that his scheduled visits to India and Japan later this month have been postponed. He was due to visit India from Jan. 13 to 16 and Japan immediately afterward. Morrison came under fire for taking a family vacation in Hawaii as the wildfire crisis unfolded in December.

He said that the governor general had signed off on the calling up of reserves "to search and bring every possible capability to bear by deploying army brigades to fire-affected communities."

Defense Minister Linda Reynolds said it was the first time that reservists had been called up "in this way in living memory and, in fact, I believe for the first time in our nation's history."

The government has committed 20 million Australian dollars ($14 million) to lease four fire-fighting aircraft for the duration of the crisis, and the helicopter-equipped HMAS Adelaide was deployed to assist evacuations from fire-ravaged areas.

The fire danger increased as temperatures rose to record levels across Australia on Saturday, surpassing 43 degrees Celsius (109 Fahrenheit) in Canberra, the capital, and reaching a record-high 48.9 C (120 F) in Penrith, in Sydney's western suburbs.

As night approached, 3,600 firefighters were battling blazes across New South Wales. Power was lost in some areas as fires downed transmissions lines, and residents were warned that the worst may be yet to come.

"We are now in a position where we are saying to people it's not safe to move, it's not safe to leave these areas," state Premier Gladys Berejiklian told reporters. "We are in for a long night and I make no bones about that. We are still yet to hit the worst of it."

The deadly fire on Kangaroo Island broke containment lines Friday and was described as "virtually unstoppable" as it destroyed buildings and burned through more than 14,000 hectares (35,000 acres) of Flinders Chase National Park. While the warning level for the fire was reduced Saturday, the Country Fire Service said it was still a risk to lives and property.

The two men killed on Kangaroo Island were identified as Clayton Lang, 43, a leading plastic and reconstructive surgeon from Adelaide, and bush pilot and safari trip operator Dick Lang, 78.

New South Wales Rural Fire Service Deputy Commissioner Rob Rogers warned that the fires could move "frighteningly quick." Embers carried by the wind had the potential to spark new fires or enlarge existing blazes.

Rural Fire Service Commissioner Shane Fizsimmons said the 264,000-hectare (652,000-acre) Green Wattle Creek fire in a national park west of Sydney could spread into Sydney's western suburbs.

He said crews have been doing "extraordinary work" by setting controlled fires and using aircraft and machinery to try to keep the flames away.

Fitzsimmons called on residents and tourists in the path of the fires to evacuate as soon as possible.

"Our message has been to make sure you leave yesterday," he said. "Leaving it until today is cutting it fine. The sooner you make that decision the better, and I would say do it now. Don't leave it any longer because the window will shrink and will shrink very quickly."

More than 130 fires were burning in New South Wales, with at least half of them out of control.

Firefighters were battling a total of 53  fires across Victoria state, and conditions were expected to worsen with a southerly wind change.  About 900,000 hectares (2.2 million acres) of bushland has already been burned through.

In a rare piece of good news, the number of people listed as missing or unaccounted for in Victoria was reduced from 28 to six.

"We still have those dynamic and dangerous conditions — the low humidity, the strong winds and, what underpins that, the state is tinder dry," Victoria Emergency Services Commissioner Andrew Crisp said.

Thousands have already fled fire-threatened areas in Victoria, and Crisp urged more people to leave. "If you might be thinking about whether you get out on a particular road close to you, well there's every chance that a fire could hit that particular road and you can't get out," he said.

 Victoria police reported heavy traffic flows on major roads and praised motorists for their patient and orderly behavior.

The early and devastating start to Australia's summer wildfires has already burned about 5 million hectares (12.35 million acres) of land and destroyed more than 1,500 homes. More acres have burned so far than in any one year in the U.S. in around seven decades, when Harry S. Truman was president.

Wildfires burning across Australia's two most-populous states Tuesday trapped residents of a seaside town in apocalyptic conditions, destroyed many properties and caused at least two fatalities.

In the southeastern town of Mallacoota, around 4,000 residents fled toward the waterside as winds pushed an emergency-level wildfire towards their homes. The town was shrouded in darkness from the smoke before turning an unnerving shade of bright red.

Victoria state Premier Daniel Andrews said there were plans to evacuate the trapped people by sea. There were grave fears remain for four people missing. "We can't confirm their whereabouts," Andrews told reporters on Tuesday.

He has requested assistance from 70 firefighters from the United States and Canada.

Victoria Emergency Services Commissioner Andrew Crisp confirmed "significant" property losses across the region.

Fire conditions worsened in Victoria and New South Wales states after oppressive heat Monday mixed with strong winds and lightning strikes.

New South Wales Police confirmed Tuesday that two men, believed to be father and son, died in a house in the wildfire-ravaged southeast town of Cobargo, while there are fears for another man missing.

"They were obviously trying to do their best with the fire as it came through in the early hours of the morning," New South Wales Police Deputy Commissioner Gary Worboys said. "The other person that we are trying to get to, we think that person was trying to defend their property in the early hours of the morning."

The two confirmed deaths raise the toll to at least 12 in Australia's wildfires, which also have razed more than 1,000 homes in the past few months.

A firefighter died Monday when extreme winds flipped his truck. Samuel McPaul, 28, was the third volunteer firefighter in New South Wales to have died in the past two weeks. He was an expectant father.

The state's Rural Fire Service Commissioner Shane Fitzsimmons said a "significant" number of properties had been destroyed.

Some communities have canceled New Year's fireworks celebrations, but Sydney's popular display over its iconic harborfront will go ahead. The city was granted an exemption to a total fireworks ban that is in place there and elsewhere to prevent new wildfires.

Hot temperatures were expected, as was the thick smoke that has shrouded views of the harbor and Sydney Opera House in recent weeks.

The popular celebrations are expected to attract around a million spectators and generate 130 million Australian dollars ($91 million) for the state's economy.

Two more people were confirmed dead and several more remain missing in Australia on Tuesday as the result of severe bushfires in the country's southeast.

"It's been confirmed today that there are two deceased persons in Cobargo and a third person remains missing with grave concerns for their safety," New South Wales (NSW) Premier Gladys Berejiklian told reporters.

Those who lost their lives are believed to be a father and son who were attempting to defend their home from an oncoming firefront in the town of Cobargo, in the southeast of the NSW.

NSW Police Deputy Commissioner Gary Warboys described the circumstances as "tragic."

"They were obviously trying to do their best with the fire as it came through in the early hours of the morning," Warboys said.

"The other person that we are trying to get to, west of Narooma, we think that person as well was caught up, trying to defend their property in the early hours of the morning. "

Meanwhile, further south in the State of Victoria four people were declared missing and more than four thousand were cut off by fire as they took shelter on the coast.

Victorian Premier Daniel Andrews said that evacuation plans were being considered for the group by any means possible.

"We've made some requests to the (Australian Defence Force) for their support, both in terms of making damage assessments but also some of these isolated communities can be accessed by sea," Andrews said.

Communities will remain on high alert throughout the night, with around 200,000 hectares ablaze in the East Gippsland region of Victoria.

At least 10 people have been killed from Australia's unprecedented wildfire season, which has destroyed an estimated 1,000 homes.

New Year's Eve fireworks in Australia's capital and other cities have been canceled as the wildfire danger worsens in oppressive summer heat, and pressure was building for Sydney's iconic celebrations to be similarly scrapped.

Temperatures on Tuesday were set to hit 38 Celsius (100 Fahrenheit) in the capital, Canberra, and 33 C (91 F) in Sydney, Australia's largest city. Thick smoke that has shrouded the city's iconic landmarks in recent months was also expected on Tuesday.

"Hot air is coming out of the center of Australia, it's particularly dry and then unfortunately conditions are expected to worsen in New South Wales as we head into Tuesday," Rural Fire Services Commissioner Shane Fitzsimmons said.

Wildfires worsened by the southern hemisphere's summertime heat have killed nine people and razed more than 1,000 homes in the past few months, with New South Wales, Australia's most populous state, bearing the brunt.

Of the 97 fires burning across New South Wales on Monday, 43 were not yet contained. Total fire bans were imposed in Sydney and other places.

The City of Sydney Council has approved Tuesday's fireworks show, although fire authorities warned it could be canceled if catastrophic wildfire conditions are declared.

The popular celebrations are expected to attract 1 million people to Sydney Harbour's famous foreshore and generate 130 million Australian dollars ($91 million) for the New South Wales economy. An estimated 1 billion people worldwide watched last year's display on television.

Australia Prime Minister Scott Morrison on Sunday said the fireworks should go ahead to show the world Australia's resiliency.

New South Wales Deputy Premier John Barilaro said the spectacle should be called off. "The risk is too high and we must respect our exhausted volunteers," he wrote on social media.

The western suburb of Parramatta decided to forego a fireworks display. "Council was not granted an exemption to proceed with its fireworks display, due to the total fire ban in place and a range of associated risks," Mayor Bob Dwyer said on Monday.

In Australia's second-most populous state of Victoria, out-of-control wildfires were forcing thousands of residents and holidaymakers to evacuate. Melbourne, Victoria's capital, peaked at 41 C (106 F) on Monday with areas southwest of the city reaching 44 C (111 F).

Lightning started 16 fires in Victoria overnight. Cooler temperatures were expected to sweep into the state late Monday, but windy conditions and thunderstorms heightened the risk of wildfires spreading.

Victoria Emergency Management Commissioner Andrew Crisp said fires had generated their own thunderstorms, creating "unpredictable and dangerous" conditions.

He said there had been no confirmed loss of properties in the region.

Victoria Emergency Services Minister Lisa Neville said the worst could be ahead. "This is not yet over. We're really only halfway through what is ahead of us here," she said.

In the national capital, Canberra, fireworks were canceled and event organizers said other activities, including live music performances, could also be canceled.

"It is a sensible decision for us not to proceed with the fireworks," the capital territory's Emergency Services Agency Commissioner Georgeina Whelan said.

Thousands of koalas are feared to have died in a wildfire-ravaged area north of Sydney, further diminishing Australia's iconic marsupial, while the fire danger accelerated Saturday in the country's east as temperatures soared.

The mid-north coast of New South Wales was home to up to 28,000 koalas, but wildfires in the area in recent months have significantly reduced their population. Koalas are native to Australia and are one of the country's most beloved animals, but they've been under threat due to a loss of habitat.

"Up to 30% of their habitat has been destroyed," Environment Minister Sussan Ley told the Australian Broadcasting Corporation. "We'll know more when the fires are calmed down and a proper assessment can be made."

Images shared of koalas drinking water after being rescued from the wildfires have gone viral on social media in recent days. "I get mail from all around the world from people absolutely moved and amazed by our wildlife volunteer response and also by the habits of these curious creatures," Ley said.

About 5 million hectares (12.35 million acres) of land have burned nationwide during the wildfire crisis, with nine people killed and more than 1,000 homes destroyed.

Fire danger in New South Wales and the Australian Capital Territory was upgraded to severe on Saturday, as high temperatures built up over the region. Sydney's western suburbs reached 41 degrees Celsius (106 Fahrenheit) on Saturday, while the inner city is expected to hit 31 C (88 F) on Sunday before reaching 35 C (95 F) on Tuesday.

Two wildfires in New South Wales are at the "watch and act" level issued by fire services.

Canberra, Australia's capital, peaked at 38 C (100 F) on Saturday, with oppressive temperatures forecast for the next seven days.

Meanwhile, New South Wales Emergency Services Minister David Elliott has gone on an overseas family vacation in the wake of Prime Minister's Scott Morrison's much-criticized family trip to Hawaii recently.

Morrison, who apologized for going away, eventually cut short his vacation and returned to Sydney last weekend.

Elliott said he will be briefed daily while overseas. "If the bushfire situation should demand it, I will return home without hesitation," he said.