A sixth tornado has hit Queensland's Bundaberg region and forecasters say more could develop, including over Brisbane, as the day wears on.
There were unconfirmed reports this morning of a tornado on the weather radar at Bribie Island.
Four people were injured when a sixth tornado hit the Bundaberg region early on Sunday, tearing roofs from some properties at Burrum Heads.
Those injured include a man who had a tree fall on him at a local caravan park, the ABC reports.
The Department of Community Safety said none of the four people were believed to have serious injuries.
Five other twisters hit the Bundaberg region on Saturday.
There were also reports of tornado activity early on Sunday at Bribie Island north of Brisbane.
It's unclear if that has caused any damage.
The Bureau of Meteorology has warned communities including Brisbane and the Sunshine and Gold coasts could be hit by tornado activity on Sunday as the low pressure system spawned by ex-cyclone Oswald moves towards NSW.
The Bundaberg Regional Council is expecting 200 homes and 100 businesses to flood on Sunday if levels in the Burnett River continue to rise, as expected.
About a dozen homes and businesses have already flooded in the city's north.
At Gladstone, north of Bundaberg, 400 properties have been evacuated near the Boyne River.Gladstone mayor Gail Sellers says the Awoonga Dam is well beyond capacity and more than eight metres of water is spilling over the dam wall - something never seen before.
''And we've still got more to come,'' she told the ABC.
Meanwhile, to the north of Brisbane, the Moreton Bay Regional Council has concerns for 4000 low-lying properties that could be at risk from a storm surge on Sunday.
Mayor Allan Sutherland says three evacuation centres have been opened on Bribie Island and at Caboolture to aid residents who might have to leave their properties.
The State Emergency Service received more than 800 requests for assistance in the 24 hours to 5am (AEST) on Sunday, most from Bundaberg south to the Sunshine Coast.
There have been several swift water rescues, with crews still working to save two people from the flooded Widgee Creek near Gympie.
Four homes have also gone under water at Woolooga, west of Gympie, the ABC reports.
In the town of Biloela, inland from Gladstone, more than 40 people were evacuated as water levels there rose.
The chaotic weather has been spawned by a low pressure system that was ex-tropical cyclone Oswald.
It's currently moving towards the Sunshine Coast, after hovering over Gladstone over the past two days.
The Bureau of Meteorology has issued severe weather warnings for communities from central Queensland down to the NSW border.
Forecaster Amber Young said there was a good chance of ongoing tornado activity, including on the Sunshine Coast, in Brisbane, and on the Gold Coast on Sunday.Strong low-level winds were feeding into the low pressure system to create conditions that spawned tornadoes.
''Considering those conditions are not only going to maintain, but possibly worsen as well, there's a realistic possibility of further tornado activity,'' Young said.