Australia's third-largest city started cleaning up stinking mud and debris on Friday after some of the country's worst floods on record, but in a sign of the task ahead, it could take six months to pump flood waters out of Queensland's coal mines.

Many suburbs in the state's capital Brisbane, a city of two million people, remained submerged after floodwaters inundated the riverside city on Thursday.

The Queensland floods, which started in December, have killed 20 people, left 53 missing and affected an area the size of South Africa. A total of 86 towns have been impacted.

We have seen a massive dislocation of people across the state, said Queensland state premier Anna Bligh, who has described Brisbane as looking like a war zone and describing what flood victims in some rural towns experienced as terror.

Right now we are still rescuing people, we are still evacuating people. So we are right in the middle of the emergency response, said Bligh.

Sodden mattresses, mud-stained clothes and water-logged electrical equipment were piled up in front of houses in the badly hit Toowong area of Brisbane.

We've lost everything. I've got my work trunk, my motorbike, my partner's car and what I'm wearing, said Steven Harrison, a builder whose wooden house had been flooded with about 1 metres of water.

Residents used pumps to remove water, and hosed down mud-strewn floors to try and stop the mud baking hard in hot sunshine. Hundreds of volunteers arrived in flooded streets to help strangers clean-up their waterlogged houses.

The massive flood which hit Brisbane was contaminated with sewage which spilt from damaged treatment plants upstream on the Brisbane River.

We need to brace ourselves, when this goes down and its going down quite quickly, its going to stink -- an unbearable stench, said Bligh. We want this mud gone out of our city as quickly as possible now, it's a big public health issue.

FLOODS STILL CUTTING COAL EXPORTS

Flooding in Queensland has brought the state's coal mining industry, which fuels Asia's steel mills, to a virtual standstill, with more than 40 mines out of action. Many mines will take weeks to pump out floodwaters from open pits.

Flooded pits and submerged rail lines have seen the state's biggest coal miners, including BHP Billiton, Rio Tinto and Xstrata. They have all declared force majeure, unable to meet export contracts.

Australia provides almost two-thirds of the world's coking coal exports, with 90 percent from Queensland, and the cut in coal exports has pushed world coal prices up by a third.

Bligh said her government would concentrate efforts to help the state coal industry meet demand in Asia, after the Commonwealth Bank estimated the floods would remove 14 million tonnes, or 5 percent, of global coking coal exports this year.

This is critical right now, to get that supply chain fully functional, Bligh told reporters.

Still, a lack of equipment means it could be up to six months before mines can return to full operation, mining contractors said.

There's just nothing left to hire, all the pumps are working non-stop, said Dave Walker, who manages water pumping for Total Water Management. It could be months before all the water is out.

Economists have estimated the flood damage at A$5 billion, with $1 billion of that to be underwritten by insurers.

The Queensland floods have been blamed on the strongest ever recorded La Nina weather phenomenon in the Pacific, which saw Australia record its third wettest year on record on 2010.

Military aircraft and trucks fanned out across Queensland, ferrying food and clothing on Friday, as weather officials warned the threat of cyclones and fresh rains could last until March. A cyclone forming in the Coral Sea was moving north into the Pacific and away from Queensland on Friday.

Flooding continued in other areas of Queensland while police evacuated communities in neighbouring New South Wales state overnight. Torrential rain in Victoria state also led to evacuations. (Additional reporting by Rob Taylor in CANBERRA and Amy Pyett in SYDNEY)