Floods left parts of Australia's third-biggest city on Thursday looking like a war zone in need of years of reconstruction, the state premier said, while fresh threats loomed with a cyclone forecast offshore.

The floods across the state of Queensland have killed at least 19 people, 12 of whom died in the Toowoomba area inland, and 61 were missing, the state government said.

Toowoomba and the Lockyer Valley region, west of state capital Brisbane, were devastated by tsunami-like flash flooding on Monday.

Large parts of Brisbane have become muddy lakes, with an entire waterfront cafe among the debris washing down the Brisbane River, a torrent that has flooded 12,000 homes in the city of 2 million and left 118,000 buildings without power.

Aerial views of Brisbane showed a sea of brown water with rooftops poking through the surface.

What I'm seeing looks more like a war zone in some places, Queensland Premier Anna Bligh told reporters after surveying the disaster from the air. All I could see was their rooftops ... underneath every single one of those rooftops is a horror story.

Floodwaters in 35 suburbs, which on Thursday peaked below disastrous levels predicted a day earlier, forced residents to take to boats to move about the streets, where traffic signs peeped above the water.

The floodwaters destroyed or damaged many parts of the city's infrastructure. One group of residents was lucky not to disappear into gushing waters when the street they were walking along collapsed.

The ground started to move and began to rumble like thunder. We all started to run as fast as we could, said Rebecca Bush. The next minute we heard this huge cracking noise that sounded like lightning had just struck. We turned around and the pathway was gone. It had completely collapsed.

An emotional Bligh said her state, reliant on farming and mining in rugged outback regions, would recover regardless of the cost and estimates that three quarters of it -- an area the size of South Africa -- was now officially a disaster zone.

We are facing a reconstruction effort of post-war proportions, she said.

Officials warned of the risk of further severe flooding in the coming weeks, with two months of the wet season ahead and already overflowing dams requiring seven days to empty to normal levels to cope with more heavy rains.

The Bureau of Meteorology forecast that a storm in the Coral Sea off Queensland's north coast would become a cyclone in 24 to 48 hours, but while it would bring fresh rains to Queensland, it was expected to move away from the coast.

The deluge has been blamed on a La Nina weather pattern in

the Pacific. Last year was Australia's third wettest on record, and weather officials forecast an above average cyclone season.

RUNNING OUT OF DRINKING WATER

Damaged water treatment plants in the Lockyer Valley mean residents were running out of drinking water, prompting authorities to order 13 water trucks to bring in supplies.

The floods could cost insurers nearly 633 million pounds and some economists expect 3 billion pounds in damage from the deluge that began last month in Queensland, crippling the coking coal industry and destroying roads, railways and bridges.

One central bank economist has warned the floods could cut gross domestic product by as much as 1 percent, a blow that would wipe A$13 billion from the economy and put at risk the government's promise of a return to surplus in 2012-13.

The floodwater peaked at almost a metre below the level of

deadly 1974 floods in Brisbane, saving thousands of homes. Despite that, many factories and homes had only roof lines visible as residents woke. Power was cut to many areas in and around the city because of fears the waters could cause electrocutions.

Boats and river pontoons torn adrift by the deluge lay piled on river banks as brown water raced past.

The flooding, which started before Christmas, continued in other areas of Queensland, with the 6,000 residents of Goondiwindi southwest of Brisbane facing a record flood on Thursday night.

This is a very eerie flood for us because we've had no rain, said Goondiwindi Mayor Graeme Scheu.

South of Brisbane, neighbouring New South Wales state has also been hit by flooding, prompting evacuations of many small residential areas, while in the southeast Victoria state has experienced flash floods and landslides.

Further north, in Queensland's coal mining heartland, one of the nation's biggest export earning regions showed signs of recovery, with coal-freight operator QR National saying its worst-hit rail network could reopen in a week.

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