Australian Prime Minister Julia Gillard Friday consoled evacuees from "devastating" floods that have swamped vast swathes of the rural northeast, affecting hundreds of thousands of people.

Gillard made a "humbling" visit to an evacuation centre sheltering refugees from the floods, which have left entire towns under water and cut off many more over an area the size of France and Germany combined.

"As devastating as these floods are, we are seeing a magnificent response by all levels of government and by emergency personnel," Gillard told reporters in Bundaberg, one of the worst-hit towns.

"The overwhelming sentiment is one of resilience and one of care and concern for their neighbours. That sense of community pulling together, that Australian sense that when times are tough we work together and look after each other."

Floods triggered by tropical cyclone Tasha have hit the farming and mining belt near Brisbane particularly hard, cutting road and rail links and crippling the region's all-important coal production.

As waters continued to rise, some 22 towns were inundated or isolated, with Bundaberg divided in two by the floodwaters and 4,000 homes in Rockhampton under threat.

Shops, homes and businesses have been swamped by the murky tide, with cars submerged and caravan parks sitting metres (yards) deep, as residents took to boats and kayaks to negotiate the waters.

About 1,200 residents evacuated the town of Emerald, population 11,000, where water was expected to engulf some 80 percent of the town as a nearby river hit record levels.

Queensland premier Anna Bligh called the situation "dire" in some parts of the state, which is facing one of its worst ever disasters and a damage bill running into several billions of dollars (several billion US).

She warned that the crisis was far from over, with some floods set to peak in the coming days and not subsiding for another week, and relief and clean-up operations lasting for weeks afterwards.

"We now have three major river systems in flood, we have 17 evacuation centres active, we have more than 1,000 people in those evacuation centres, and many more thousands staying with relatives and friends," Bligh said.

"And we've still got major places like Rockhampton with floodwaters coming down the river and what may well be the biggest flood they've ever experienced. So a lot more to go before we can really say we're in full recovery mode."

On Friday, Bundaberg's port was closed to all shipping because of choking detritus washed downstream, while Rockhampton airport was expected to be shut over the weekend.

Industry giants Rio Tinto and BHP Billiton are among a group of companies to announce production problems at mines churning out nearly a quarter of Australian hard coking coal exports -- much of it bound for Asian steel mills.

Huge quantities of ruined crops are expected to send prices of bananas, mangos and sugar soaring, while officials are concerned over food shortages in isolated areas and possible disease outbreaks from contaminated water.

Meanwhile forecasters warned that another cyclone was forming off Western Australia, on the other side of the huge country, while extreme heat posed a wildfire risk in South Australia and Victoria over the New Year holiday.