Four were killed in Toowoomba, a town west of the  Queensland state capital of Brisbane, after heavy rains sent a  2-metre wall of water through streets on Monday, carrying away  cars and pedestrian TV footage showed swirling brown floodwaters gushing  through the centre of Toowoomba laden with debris, as people  clung to telephone poles and rooftops to survive. There are growing fears the floods could soon hit Brisbane, a city of 2 million people.

"This is going to be I think a very grim day, particularly for the people in that region, and a desperate hour here in  Queensland," Queensland Premier Anna Bligh said on Tuesday.

"Right now we have every possible available resource deployed into this region to search for those people that we  know are missing," she said.

Two women and a child were killed at Grantham, a township between Toowoomba and Brisbane. Nearby at Withcott, police said nine people are missing there, with the death toll set to  rise.

Police said more than 40 people were plucked from rooftops  by helicopter overnight, while additional helicopters and  military personnel were to begin searching for more than 70  people reported as missing in the Lockyer River valley.

The floods in Queensland that started after heavy rains  before Christmas have caused around $5 billion of damage after  destroying homes, roads and rail lines, as well a paralysing  the state's key coal mining sector.

"I personally believe it will get worse today," Queensland Disaster Coordinator Deputy Commissioner Ian Stewart told Australian television.

Bligh said a major incident room had been set up in Brisbane to coordinate a rescue operation.

The worst floods in 50 years have at times covered an area   the size of France and Germany combined.  At least 12 people have been killed, while dozens of towns have been isolated or partly submerged, with more rains expected.

Flooding was expected to reach Brisbane, where hundreds of homes and businesses in 32 suburbs along the swollen Brisbane River and further west were under threat.

Authorities have made sand bags available for residents after some experts described conditions as similar to when the city was hit by deadly floods in 1974.