Large swaths of Australia's southeast were on high alert for major flooding on Saturday after torrential rains caused rivers to break their banks, with meteorologists warning of more severe weather ahead.

A low-pressure system has dumped 50 to 150 millimetres (2-6 inches) of rain in some areas of Queensland and New South Wales since Thursday, for some the highest in years, Australia's Bureau of Meteorology said.

Flood warnings were issued for numerous rivers across parts of Queensland and much of inland New South Wales, with the greatest concern for regions along the Lachlan River in the central west of New South Wales, Australia's most populous state.

"We're bracing for major floods," said Phyllis Miller, the mayor of Forbes, a town of 8,500 on the Lachlan River, according to the Australian Broadcast Corporation.

There were concerns about major flooding in eastern Victoria state, with meteorologists saying flood watches were issued for much of the area. More rains and wild weather were expected throughout the weekend.

"Damaging winds may bring down trees and power lines," Dean Narramore, a meteorologist said in a video message on Twitter.

Victoria State Emergency Service reported dozens of calls for help throughout the eastern part of the second-most populous state since Friday, mainly from people stranded in their cars in flash floods.

A family of four travelling across Australia since November 2020 was stranded in South Australia's outback after torrential rain bogged their campervan, the ABC reported.

"The vehicle from Western Australia containing two adults and two children became stranded after bad weather and flooding on the roads," the ABC cited a police spokesperson as saying.

"They are safe and well and in contact with the police."

(Reporting by Lidia Kelly; Editing by William Mallard) ((Lidia.Kelly@thomsonreuters.com;))