9 killed in Australia's flood 'tsunami'

A tsunami like tidal water waves ripped through an Australian valley, killing at least nine people, including four children, as cars and trees were tossed around and military helicopters soared above to search for 72 people reported missing.

The unprecedented floods smashed through Queensland state as 150 ml of rain from freak storm turned into a raging stream, hurling gallons of water down the Lockyer valley, uprooting homes and trees.

The torrent which formed into flash floods stormed downstream towards the state capital of Brisbane, where authorities ordered an emergency evacuation of more than 2 million people.

"We now have confirmation of eight dead, including the death of young children," Queensland Premier Anna Bligh said.

Four of the dead were children, some of them swept away in cars driven by their mothers.

Officials have said the death toll would rise "potentially quite dramatically", as whole families were missing and rescue efforts were hampered by heavy rain and washed-away roads.

Prime Minister Julia Gillard warned the country to prepare for the worst after flash floods smashed mountainside Toowoomba, which lies 125 kilometres west of the state capital, Brisbane, the Australian reported.

She described the incident as an "unfolding human tragedy".

"We are very likely to hear of more confirmations of missing people in the next couple of hours," she said.

TV images showed Toowoomba's streets turned into churning rapids dotted with floating cars, some with people sitting on top, while elsewhere residents were forced onto roofs as waters lapped at awnings.

Toowoomba mayor Peter Taylor said this morning the flash flooding that swept through the Queensland city could not have been planned for and was "unprecedented".

Authorities say the flood threat facing Brisbane and Ipswich is worse than the 1974 disaster.

In 1974, the Brisbane River broke its banks and inundated the city, killing 14 people and flooding almost 6,000 home.

The flood followed months of rain which had filled rivers in the south-east, then when Cyclone Wanda dumped heavy rain over the region these rivers were pushed over the limit, leading to the worst floods of the century.