Flooded residents in Australia are being told to stay out of the water due to concerns of attacks by snakes and crocodiles.

Authorities warned residents of the coastal city of Rockhampton in Queensland after reports of saltwater crocodiles in the Fitzroy River and unusually high numbers of snakes.

The river, which runs through Rockhampton, has spilled over its banks, flooding houses and businesses in water ranging from a few inches to waist-deep. There have also been warnings of fast-moving currents powerful enough to drag cars from roads.

Australia's biggest floods in decades have spread across a swathe of land the size of France and Germany combined, leaving some towns submerged and others isolated.

The city of Rockhampton was completely cut off and accessible only by boat or helicopter and residents of 500 houses have been evacuated.

Now the 75,000-strong population are bracing themselves, as the floods are expected to get worse in the next 24 hours. Authorities warn the Fitzroy River is expected to reach its peak of 9.4 meters on Wednesday.