A flood of "biblical proportions" that has consumed much of northeastern Australia is moving towards the coast, with rising waters along one river threatening a city of 75,000 people.

The flooding, which now covers an area larger than France and Germany combined, has reportedly also claimed two lives.

Australian police said a 41-year-old woman drowned while trying to cross a flooded causeway this weekend.

She had been travelling in one of two cars that were swept into a river in Burketown, in western Queensland, on Saturday night. Her body was recovered two kilometres away on Sunday.

"We're just grateful there weren't more casualties," Queensland's Acting Assistant Police Commissioner Alistair Dawson told The Associated Press. "We're focused on preventing any more."

A 38-year-old man also drowned Saturday after he was swept off a small boat along the Boyne River, The Brisbane Times reported. Police recovered the man's body on Monday morning local time, the paper said.

Days of pounding rain in the region have overflowed into low-lying communities, affecting 200,000 people and forcing the evacuation of several coastal communities.

On Monday, Australian Prime Minister Julia Gillard offered emergency relief to those affected by the sea of flood waters. The assistance includes low-interest loans for farmers whose lands lie submerged.

"This is a major natural disaster and recovery will take a significant amount of time," she said in a statement.

The city of Rockhampton, which has a population of 75,000, has been largely cut off from the outside world. The airport has been closed and the highway to the state capital of Brisbane severed.

The city had been partially evacuated by Saturday, as officials warned the Fitzroy River flowing through Rockhampton would continue to rise until Tuesday or Wednesday.

"We are just sitting here watching this river rise," Mayor Brad Carter told CTV News Channel in a phone interview on Sunday. "It is filling up low-lying areas. We have had a number of people that we have had to evacuate."

Carter said the airport had to be closed because runways had turned into shallow rivers and about 500 residents have been forced to leave their homes.

About 40 per cent of Rockhampton sits on a low-lying shelf that is expected to slip underwater through the week. Carter says they expect the body of floodwater to reach the city on Wednesday.

"The river behaves in a reasonably organized sort of a way, so we can predict with some level of certainty what level of water will get here," Carter said. "What we don't know is when the water breaks its banks, which it has done for a couple of days now, it is hard to predict where the water will go and where it will rise."

Evacuation centres were becoming home to refugees across the state, many of who may not be able to return home for up to a month, according to Dawson, the assistant police commissioner.

"It's hard to make the call that the worst is behind us. It's a unique event -- parts of the state are still in response mode while others are in recovery. I think we're in the middle of the event," he said.

Officials estimate that half of Queensland's 1.8 million square kilometres has been affected by the flooding. Queensland Premier Anna Bligh warned that cleanup efforts were expected to cost billions of dollars.

And the worst might not be over for the area, with a severe thunderstorm expected to sweep through the southern region, bringing with it damaging hail and the potential for flash flooding.

Warren Bridson, with Emergency Management Queensland, said the region is expected to be hit by as many as five cyclones this year.

"We were warned some months ago by our bureau of meteorology to expect more severe weather this season because of La Nina, and that's exactly what's happened. We've had our first cyclone," Bridson said.

"We do expect more," he added. "This is the beginning of what we call our wet season."

With files from The Associated Press