Climate change activist Greta Thunberg has taken a swipe at Australia's leaders as the bushfire disaster rages on.

The teen, who celebrated her 17th birthday on January 3, took to Facebook earlier today to share a horrific image of a kangaroo fleeing flames as a fire engulfs a home.

In her caption, she offered words of support to Australian bushfire victims and also took aim at the government's lack of action on climate change.

"Australia is on fire. And the summer there has only just begun. 2019 was a year of record heat and record drought. Today the temperature outside Sydney was 48.9°C," she wrote.

"500 million (!!) animals are estimated dead because of the bushfires. Over 20 people have died and thousands of homes have burned to ground. The fires have spewed 2/3 of the nations national annual CO2 emissions, according to the Sydney Morning Herald. The smoke has covered glaciers in distant New Zealand (!) making them warm and melt faster because of the albedo effect.

"And yet. All of this still has not resulted in any political action. Because we still fail to make the connection between the climate crisis and increased extreme weather events and nature disasters like the #AustraliaFires."

Thunberg said made an impassioned call for action.

"That has to change. And it has to change now," she posted.

"My thoughts are with the people of Australia and those affected by these devastating fires."

Within hours, her post has attracted thousands of likes, shares and comments.