Tidal wave of mud kills Australians (VIDEO)

A tidal wave of mud and water enveloped a major Australian city on Monday, sweeping four people to their deaths. Another three children are missing.

Footage of the floods in the Lokyer Valley, near Brisbane, the country's third-largest city, show cars and vans being thrown around as bystanders gasped in horror.

A region the size of Britain, France and Germany combined has been hit by the worst floods in a generation in the past two weeks.

Residents in Brisbane sandbagged their homes against rising waters on Monday as torrential rain worsened floods that have cut off entire cities and battered the economy of the northeastern state of Queensland.

Six people have been killed while dozens of towns have been isolated or partially submerged. More monsoon rains are expected all week. The floods have caused an estimated $6 billion in damage and economists say they will cut economic growth in 2011 and heighten inflation as food prices rise and reconstruction begins.

Emergency workers in Brisbane, a city of 2 million, handed out sandbags to people in low-lying areas and warned the worst of the flooding might not occur until Tuesday or Wednesday.

Toowoomba, a major rural city west of Brisbane, was hit Monday by a two-meter-deep wall of mud-filled floodwater, police said.

More dramatic television footage taken from a helicopter above the deluge showed a family of three who had climbed onto the roof of their four-wheel-drive vehicle that was being tossed around violently. Neither the people, nor their car, have been sighted since the helicopter left the scene to pick up nearby rescue personnel.

Authorities are desperately searching for many others missing. The police have urged motorists to stay off the roads in the southeast part of the state.

Click here to listen to live coverage of the floods.