The Premier, Campbell Newman, made the declarations as Gladstone began mass evacuations in the face of unprecedented rain expected over the next 24 hours.

All beaches from Tannum Sands, on the central Queensland coast, south to the NSW border are closed.

The tornadoes injured 17 people and damaged 150 properties.

Queensland Police warned of quick rising water in the Baffle Creek catchment, about 80 kilometres north of Bundaberg last night, with Mimdale identified as a major flooding risk.

The first tornado struck the coastal town of Bargara about 1pm, bringing down power lines, tearing off roofs and smashing windows. A man and a woman were seriously injured when their car was crushed by a falling tree. Both were flown to Brisbane in a critical condition.

The Queensland Emergency Services Minister, Jack Dempsey, told Fairfax Media a triage centre had been set up in Bargara to treat 15 people hurt by flying glass and debris.

''The fact that these tornadoes are completely unpredictable … we can't say whether they're finished or whether more are coming,'' he said.

In Gladstone, about 2000 were set to evacuate on Saturday afternoon. A major flood emergency warning was issued by the SES for Winfield, as Baffle Creek was expected to rise above the 1971 record. Warnings were also issued for the Calliope, Kolan and Boyne rivers with the latter expected to swell to one-in-100-year levels.

Meanwhile, Brisbane was on standby on Saturday for its worst flooding since the disaster of 2011.

with Anne Tarasov