Australia's Queensland flood crisis has escalated as many towns in southern Queensland have been devastated by Monday's unprecedented flash flooding.

A flash flood hits Toowoomba, Queensland on January 10, 2011. (Xinhua/AFP photo)

Bligh said many people remained unaccounted for in the Lockyer Valley towns of Murphy's Creek, Grantham and Withcott, west of Brisbane and poor weather continued to hamper rescue efforts.

The wall of water is making its way to Brisbane, where rain and storms are lashing the city and the biggest flood since 1974 is expected to arrive in the next two days.

Bligh said the situation in Brisbane and Ipswich, a suburb 40 km south-west of Brisbane, was very serious.

"Ipswich and Brisbane are now facing their greatest threat and toughest test in more than 35 years," she said.

"Current predictions indicate the river will continue to rise into Thursday with flood levels expected to be higher than the 1974 peak," Bligh said.

"Now is not a time for panic, now is the time for us to stick together," the state Premier said.

Deputy Police Commissioner Ian Stewart said that a disaster declaration had been made for the lower half of the state to include the greater Brisbane area.

Brisbane Lord Mayor Campbell Newman said on Tuesday that a total of 6,500 homes and businesses in Brisbane are expected to experience direct, "significant" flooding and would affect 14,900 people, as forecasts show.

The mayor said a further 16,500 properties would be partially affected by flooding.

"There are 80 suburbs that will be impacted one way or another, " the mayor said, adding "there will be flooding in the city on Thursday afternoon if these projections are right."

The flood crisis has affected much of Queensland since the end of last year. Economists here said that the flood will bring about billions of dollars of damage to Australian economy.

VietNamNet/Xinhuanet