One person has died and another is missing as wildfires continue to burn across three Australian states.
Firefighters work to extinguish a bushfire in Dargan, some 120km from Sydney, on 18 December 2019. Photo: Saeed KHAN / AFP
In New South Wales, sudden southerly winds fanned the flames of more than 100 blazes and fire officials said a man who had chosen to stay at his property could no longer be contacted.
Saturday had been an "awful day", NSW fire chief Shane Fitzsimmons said.
Prime Minister Scott Morrison has cut short a holiday in Hawaii after being criticised for leaving amid the crisis.
Earlier acting prime minister Michael McCormack conceded that more had to be done to tackle global warming, after many Australians linked the severity of this year's fires to climate change.
Since September, Australia's bushfire emergency has killed at least nine people, destroyed more than 700 houses and scorched millions of hectares.
What happened on Saturday?
Rising temperatures and strong winds worsened fires in three states.
In South Australia one person was found dead, another was critically injured and 15 homes had been destroyed about 40km east of the state capital of Adelaide.
In New South Wales a man was missing in the Blue Mountains west of Sydney after towns in the area were hit by an ember attack - when burning vegetation is blown ahead of the main blaze and starts new fires.
However the southerly winds later eased and by Saturday evening six fires in the state were deemed to be at emergency level - the second highest level of danger after catastrophic - including two near Sydney.
In Canberra a cricket match was called off because of poor air quality resulting from smoke from the fires.
New South Wales leader Gladys Berejiklian urged Christmas travellers to delay their journeys.
"We are asking everybody not to travel on roads anywhere near the vicinity of an active fire unless you absolutely have to," she said.
In Victoria, authorities said 142 fires had started in the state since Friday. One of these was burning at an emergency level by Saturday afternoon.
What is driving the fires?
A combination of temperatures above 40C, low humidity and strong winds have worsened the struggle for the 3,000 emergency personnel mobilised to deal with the bushfires in NSW.
"We are in a period of unbelievable drought and some areas haven't seen rain for more than 12 months", NSW Rural Fire Services Inspector Ben Shepherd told the BBC.
"These fires are likely to continue to spread well past Christmas", he added.
Some of the fires in NSW were generating their own thunderstorms, the Rural Fire Service said.
Conditions were expected to improve over the next few days ahead of another period of hot weather expected next week.
"We will not get on top of these fires until we get some decent rain - we have said that for weeks and months," Mr Fitzsimmons said.
However weather officials say no major rainfall is expected in the next two months.
The Gospers Mountain mega fire has destroyed about 460,000 hectares (1.14 million acres) north-west of Sydney and fire officials said there was a risk it could merge with the Grose Valley fire in the Blue Mountains.
What travel warnings have been issued?
The states of NSW and South Australia are the focus of the travel warnings.
In NSW, several major roads and highways have been closed, including a section of the Princes Highway.
As of 3am (5am Sunday NZT), 22 roads and highways in NSW were affected by fire, according to a government website.
Roads have been closed in South Australia as well, with residents asked to monitor the government traffic website for updates.
"If members of the public attempt to enter the areas, they will be turned away, regardless of being property owners or business owners, due to specific safety reasons," a police official said.
Who are the victims?
Tributes have been paid to firefighters Geoffrey Keaton, 32, and Andrew O'Dwyer, 36, who died when their truck was hit by a falling tree near a fire front, causing it to roll off the road.
Three other firefighters who were also in the vehicle survived with minor injuries.
NSW fire commissioner Shane Fitzsimmons said firefighters everywhere were grieving over the "huge loss" of the two young fathers, who were caught up in "the worst imaginable set of circumstances".
"[They] simply went out, doing a remarkable job, like all their colleagues, and like they have done year-in, year-out, and to not be coming home after their shift is a tremendous grief," he said.
South Australian Premier Steven Marshall said a person had been killed in Murraylands, when the car they were driving hit a tree. Another person died in the Charleston area of the Adelaide Hills, authorities said.
Why is Morrison facing pressure on climate change?
Many Australians have accused Prime Minister Scott Morrison's government of inaction on climate change.
Last year, the UN reported that Australia was not on track to meet its commitments under the Paris Agreement - the global deal to tackle rising global temperatures.
Scott Morrison, the Prime Minister of Australia. Photo: AFP / Getty Images
Firefighters' union leader Leighton Drury said Australia was "seeing an absolute lack of leadership from this government and it is a disgrace".
Criticism grew as a heatwave broke records across the country and exacerbated mammoth blazes, making the task even harder for exhausted firefighters - many of them volunteers.
McCormack acknowledged that further action must be taken to combat climate change but said there was "a lot of hysteria" surrounding the issue.
"Climate change is not the only factor that has caused these fires. There has been dry lightning strikes, there has been self-combusting piles of manure, there has been a lot of arsonists out there causing fire," he said.
Although climate change is not the direct cause of bushfires, scientists have long warned that a hotter, drier climate would contribute to Australia's fires becoming more frequent and more intense.
- BBC