Residents are stacking sandbags to protect low-lying properties ahead of a tropical cyclone that is forecast to become the first in 51 years to hit the Australian east coast near Brisbane, the nation’s third-most populous city.

Millions of residents along Australia’s eastern coast are preparing for the impact of the most southerly cyclone to threaten the region in more than five decades.

Australia's east coast braced on Wednesday for a tropical cyclone that is swirling towards Brisbane, the country's third-most populous city, as authorities warned thousands of properties were at risk due to strong winds and flash flooding.

Tropical Cyclone Alfred is forecast to cross the coast between the Queensland state capital Brisbane and the tourist city of Gold Coast to the south late Thursday or early Friday.