Australian Prime Minister Malcolm Turnbull has activated a disaster response plan after a powerful cyclone pummelled the north-east coast.
Cyclone Debbie caused major damage, torrential rain and power cuts to tens of thousands of homes.
Defence force helicopters and naval vessels carrying aid are to be despatched to Queensland.
Mr Turnbull said one death had been confirmed but added that emergency crews had yet to assess the damage.
Cyclone Debbie made landfall between Bowen and Airlie Beach as a category four storm, whipping gusts of up to 263km/h (163mph).
It is moving inland as a category two storm but could cause more damage.
"Conditions have deteriorated rapidly," Mr Turnbull told parliament. "Take care and stay safe. Be prepared to shelter in place until Wednesday."
He said the government would be urging insurance companies to be "compassionate" and supportive of people who had claims to make following the cyclone.
The extent of Cyclone Debbie's devastation, which has a 50km-diameter eye wall, may not be known for some time, the authorities said.
Queensland Police Commissioner Ian Stewart said the storm's slow speed had created a "battering ram effect", adding: "We are going to get lots of reports of damage, and sadly I think we will also receive reports of injuries, if not death."
Mr Stewart said the weather had contributed to the death of a woman in a car crash on Monday.
One man was seriously injured when a wall collapsed in the town of Proserpine.
Queensland Premier Annastacia Palaszczuk said assessing damage was difficult because communities had been cut off from power and phone reception.
"Everyone is going to be in shock tomorrow, just to see the full impact of this cyclone," she said. "I'm bracing myself for it."
More than 2,000 emergency workers are on standby, but people have been warned crews will only respond when it is safe to do so.
Officials warned people to stay indoors until it was safe to go outside, while electricity providers said it was not known when power would be restored to houses.
"We're going to see the impact of Cyclone Debbie for the next three to five days," Ms Palaszczuk said.
She also condemned people spotted surfing during the cyclone as "irresponsible" and "ridiculous".
More than 25,000 people were urged to evacuate their homes ahead of predictions the cyclone would be Queensland's most damaging since 2011.
One person in the Whitsunday Islands compared the winds to "freight trains coming through left and right".
"The trees are going wild," the man, identified only as Charlie, told the Australian Broadcasting Corp. "The place is just shaking continuously."
In other developments:
Police warned people to beware of fallen power lines, which could be deadly
The Insurance Council of Australia declared the cyclone a "catastrophe"
The Great Barrier Reef Marine Park Authority said it feared Debbie might have caused extensive damage to reefs in its path