Australian star Nicole Kidman and American singer P!nk have each donated $500,000 to local fire services after witnessing the devastation across the country.

Kidman and husband Keith Urban took to Instagram to announce their cash boost as they urged their fans to donate.

"Our family's support, thoughts and prayers are with everyone affected by the fires all over Australia," Kidman wrote.

"We are donating $500,000 to the Rural Fire Services who are all doing and giving so much right now."

In a post to Instagram, music superstar P!nk, who has toured and holidayed many times in Australia with her family wrote: "I am totally devastated watching what is happening in Australia right now with the horrific bushfires.

"I am pledging a donation of $500,000 directly to the local fire services that are battling so hard on the frontlines. My heart goes out to our friends and family in Oz."

Comedian Celeste Barber has so far raised a staggering $20 million for volunteer firefighters with an online campaign just a day after it was launched.

More than 50,000 people worldwide have pledged money to the NSW Rural Fire Service after Barber issued a plea for donations on Facebook.

Australian stars and members of the royal family, including Prince Harry and Meghan Markle, have also delivered messages of hope on social media, urging followers to donate to charity.

The Duke and Duchess of Sussex recalled their trip to NSW in 2018 in their Instagram post, using the environmental crisis term "Ecocide" to describe the bushfires.

Prince William and Catherine, the Duchess of Cambridge, also told of their shock and sadness.

In her statement, the Queen said she and Prince Philip were sending their "thoughts and prayers to all Australians at this difficult time".

"I have been deeply saddened to hear of the continued bushfires and their devastating impact across many parts of Australia," she said. "My thanks go out to the emergency services, and those who put their own lives in danger to help communities in need."

Aussie star Dannii Minogue also posted about the tragedy, urging followers to donate via the local Melbourne charity St Kilda Mums.

Sophie Monk called on her Instagram followers to donate to the Red Cross, Wires Wildlife Rescue and the Salvation Army.

"Our people and animals need help," she posted. "One thing I love about Aussies, we always have each other's backs."

Other big name donors include Hugh Jackman, who posted a haunting image of a child wearing a face mask against the backdrop of a blood-red sky, Lleyton Hewitt and TV presenter Kylie Gillies.

Barber posted images of her mother-in-law's house in Eden on the NSW South Coast, which has been severely affected by the bushfires.

"It's terrifying. They are scared. They need your help," she wrote.

Barber's family has been ordered to evacuate from the area.

A day after her plea, Barber was overwhelmed by the response.

"This is out of control! You are all out of control," she wrote.

"My love and appreciation for you all is out of control.

"Unfortunately today the fires are due to get even more out of control."

AFL WAG and businesswoman Rebecca Judd has also donated $50,000 through her activewear label Jaggad, which is hosting a fundraiser for the Red Cross.

Fashion designer Alex Perry has announced 100 per cent of sales online and instore for a week will go to the NSW RFS.

Sporting stars Ben Simmons and Nick Kyrgios are also among a host of Aussie celebrities helping to raise millions for our volunteer firefighters and communities.

An emotional Kyrgios made a $4000 donation from his first match of the ATP Cup, after serving 20 aces in a win over Germany's Jan-Lennard Struff. The world No.30 had earlier pledged $200 per ace towards fire relief.

In his post-match interview Kyrgios spoke of how he had been affected by the fires.

"It's tough to go out there and concentrate on tennis ... Every ace I was hitting, that was all I was thinking about. Every time I stepped up to the line, that was all I was thinking about." he said.

Meanwhile, world number 2 tennis star Novak Djokovic has expressed concern over poor air quality in Melbourne in the lead up to the Australian Open, which kicks off on January 20.

Djokovic said it was reasonable to consider delaying the start of the tournament because of the extreme conditions "but I think that's probably the very, very last option for anything.

"I think they're going to try to do anything to not delay anything in terms of days and when it starts," he told a news conference. "But if it comes down to ... those conditions affecting the health of players, I think we should definitely consider it."

Djokovic said the players' council for the men's tour "would discuss it for sure" if conditions get worse, adding that players had in the past dealt with poor air quality at some tournaments in China and elsewhere, "but this is something different."

"So I really never had this kind of experience before," he said. "I hope that it's going to dissipate, that this is something that is very temporary."

Djokovic also supported the ATP Cup's decision to donate $100 to the Red Cross for every ace served during the cup, an initiative that is expected to raise over $150,000.

Two days ago, he visited the Lone Pine Koala sanctuary to help raise awareness about the animals' endangered habitats.

NBA star Ben Simmons also wrote of his sadness at the unfolding situation.

"I'm so sad by the loss our country is currently facing. The images of the raging fires, people, families, firefighters and wildlife are nothing short of terrifying," he wrote on Instagram.

"I am working with my family and calling on my Australian NBA brothers and any others that can, to do our part to help in this catastrophic disaster, not just for today but to support communities in their eventual rebuild when the fires have stopped. Australia is a strong and resilient country and I urge you all to be brave, kind and compassionate to each other through this extremely hard time."

Cricketer Chris Lynn is another raising money through his sporting endeavours.

"For every six I hit in this years Big Bash League I will donate $250 towards the Red Cross Bushfire Appeal. It is special to see so many athletes from various sports getting in behind the real heroes who are fighting to save lives and properties around our country. Any players, businesses or sponsors are more than welcome to be involved - let's do our best to help our community," he wrote.

With the fires receiving worldwide attention, global celebrities have also had their say, including actress Bette Midler.

Other international and Australian stars have also posted about the fires.

Miranda Kerr posted: "Sending love and prayers to those affected by the Australia Wild Fires. It's absolutely heartbreaking.

"Please join me in supporting those affected and visit the link in my bio to donate to the Red Cross Disaster Relief and Recovery Fund.

All donations will support affected families and the community during this disaster. Thank you to the brave fire fighters and community of volunteers for your help and support."

Kim Kardashian West and her sister Kourtney have posted on Instagram, calling on followers to help by donating money to local fireys.

Rapper Chris Brown posted on Instagram a message from a fan pleading with him to help raise awareness about the fires.

Kelly Rowland, former member of Destiny's Child and a popular host on The Voice Australia, posted a video to Instagram sending Australians her thoughts and prayers.