Thousands of residents in the sludge-soaked Australian city of Brisbane joined military personnel for a clean-up effort dubbed "Salvation Saturday," following widespread floods that have ravaged the state capital of Queensland.

While Brisbane attempted to mop up, heavy rain prompted four other states to issue new flood warnings. Other parts of Queensland also remain under water as officials anxiously watch swollen rivers for signs of relief.

In Brisbane, the country's third-largest city, some of the flooding has receded, leaving behind a smelly sludge and nearly 30,000 damaged homes and businesses.

Armed with mops, buckets and shovels, locals are also getting their first look at the damage, which is pegged in the billions of dollars.

"Everybody rolls up their sleeves in this town," said Brisbane Mayor Campbell Newman, as he praised Saturday's large volunteer turnout.

Still, some areas of the city have been harder hit since the Brisbane River burst its banks several weeks ago, and about 28,650 homes still have no power, according to the local utility provider.

It's believed that parts of the power grid have been damaged or washed away, and it's not clear when the lights will go back on in many areas.

Since the flooding began in November, 26 people have died in Queensland. Another 28 are still reported as missing, many of whom vanished after a series of flash floods that tore through communities west of Brisbane on Monday.

Heavy rain has also led to flooding in parts of Queensland's east coast, and more evacuations have taken place in the southern state of Victoria, which is the most densely populated area in the country.

At least three communities on the island state of Tasmania have also been evacuated.

The Queensland floods could end up costing an estimated $13 billion (all figures Australian), which is about 1 per cent of the country's gross domestic product.

The economic toll is also rising, as coal mining companies struggle to reach production quotas. Widespread crop destruction in Queensland could also result in higher global food prices.

Weather forecasters warn that cool, wet weather could last through until March, as a La Nina weather system remains lodged in the central Pacific equatorial region.

Meanwhile, as the tennis world flies to the country for the Australian Open, stars like Roger Federer and Rafael Nadal threw their support behind the "Rally for Relief" event in Melbourne Sunday.

With files from The Associated Press