Flooding on Australia's east coast claimed another life overnight, bringing the death toll from the extreme weather to six as a "rain bomb" continued to move south Sunday.

Police in the state of Queensland said a 34-year-old man had died after his car became submerged in floodwaters around 2:30am on Sunday (1530 GMT Saturday).

While the man was able to free himself from his vehicle and tried to swim to safety, he failed to surface and his body was found a short time later.

Huge downpours have battered eastern Australia for the better part of a week, unleashing decades-high floods, inundating homes and roads, and sweeping away cars.

Adrian Schrinner, lord mayor of Queensland's capital city Brisbane, described the weather system as a "rain bomb above South East Queensland".

State premier Annastacia Palaszczuk pleaded that people living in Brisbane stay home as the weather system moved south Sunday into major residential areas.

"This water is unrelenting at the moment," she said.

With intense rain expected to continue into next week, more than 1,400 homes in Brisbane were at risk from the floodwaters, she said.

The Australian Bureau of Meteorology has issued flood warnings for vast swathes of Queensland and northern New South Wales, with more than 300 mm (11.8 inches) falling in some areas in the last 24 hours.

Police continue to search for a man in his 70s who fell into the Brisbane River on Friday.