Powerful winds and sweltering heat on Saturday combined to intensify catastrophic bushfires across Australia, forcing more than 100,000 people to evacuate their homes as firefighters struggled to contain the "virtually unstoppable" blazes ravaging large swaths of the continent.

At least two dozen people and an estimated half a billion animals have been killed by the fires, which have scorched more than six million hectares of land since September.

Australian authorities said Saturday and Sunday are likely to be two of the worst days since the fire season began late last year. "We are still yet to hit the worst of it," warned New South Wales Premier Gladys Berejiklian.

As the Associated Press reported Saturday, "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."

According to CNN, three fires in the Omeo region in Victoria state combined overnight "to form a single blaze bigger than the New York borough of Manhattan."

Angus Barners, an incident controller at the Rural Fire Service in Moruya, NSW, told CNN that "we can't stop the fires, all we can do is steer them around communities."

Prime Minister Scott Morrison—who has faced fierce criticism from residents for failing to take sufficient action to confront the blazes—announced the 3,000 Australian Defense Force Reserve troops Saturday to help fight the devastating fires.

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