One of the most powerful cyclones on record began pounding Australia's northeast coast, threatening popular tourist cities and with people scrambling to find refuge after police turned them away from overcrowded shelters.
Cyclone Yasi, packing winds of up to 300 km (186 miles) an hour near its core, started to come ashore along hundreds of km of coastline on Wednesday night, giving a foretaste of a storm centre described by authorities as "terrifying".
"Tonight we need to brace ourselves for what we might find when we wake up tomorrow morning," Queensland state premier Anna Bligh said.
"Without doubt, we are set to encounter scenes of devastation and heartbreak on an unprecedented scale. This cyclone is like nothing else we've dealt with before as a nation,"
Yasi is a maximum-strength category five storm, on a par with Hurricane Katrina which wrecked New Orleans in 2005.
Its centre is expected to hit land a little after midnight (1400 GMT).
Selwyn Hughes, turned away from a shopping centre acting as a shelter, stood with his family in the centre's uncovered car park and said his only comfort for the moment was in numbers.
"There are so many of us here. Surely they have to do something, find somewhere safer to move us to before it arrives," he said, squatting on a pink suitcase with his five children, aged two to 13.
Engineers warned that Yasi could even blow apart "cyclone proof" homes when its centre moved overland, despite building standards designed to protect homes from the growing number of giant storms.
Bligh said the cyclone could batter the state for up to three days as it moves inland and slowly weakens. She said 37,000 homes have already lost electricity.
The greatest threat to life will likely come from surges of water forecast at up to seven metres above normal high tide levels in the worst-affected coastal areas. Waves of 6.6 metres have already been recorded about 20 kms out from Townsville.
More than 400,000 people live in the cyclone's path, including the cities of Cairns, Townsville and Mackay. The entire stretch is popular with tourists, includes the Great Barrier Reef, and is home to major coal and sugar ports.
In Townsville alone, the storm surge could flood up to 30,000 homes, according to the town's web site. The tourist hub of Cairns also expects its city centre to be flooded.
The military is helping evacuate nearly 40,000 people from low-lying coastal areas, and from the two hospitals in Cairns.
Satellite images showed Yasi as a massive storm system covering an area bigger than Italy, with the cyclone predicted to be the strongest ever to hit Australia.
Mines, rail lines and coal ports have all shut down, with officials warning the storm could drive inland for hundreds of kilometres, hitting rural and mining areas still struggling to recover after months of devastating floods.
Yasi threatened to inflate world sugar, copper and coal prices, forcing a copper refinery to close and paralysing sugar and coal exports. It even prompted a major mining community at Mt Isa, almost 1,000 km inland, to go on cyclone alert.
Global miners BHP Billiton and Peabody Energy
have shut several coal mines located in Queensland ahead of the cyclone, an official for the union representing Queensland coal miners told Reuters.
Prime Minister Julia Gillard has put 4,000 soldiers based in the garrison town of Townsville on standby to help once the cyclone passes, as well as military ships and helicopters.
Hundreds of people were lining up in a supermarket on the western side of Cairns, stocking up on staples such as bread, milk and tinned goods.
The centre of the cyclone is expected to make landfall between Cairns and Townsville. Yasi knocked out meteorology equipment on Willis Island in the Coral Sea, 450 km east of Cairns.
In Cairns, main streets were deserted. Shops were closed and windows taped to stop glass from shattering.
"We're hoping for the best, but expecting the worst to be honest," Scott Warren said as he covered windows with black plastic sheeting at a coffee shop on the Cairns waterfront.
State premier Bligh warned that the mobile phone network may go down and said current estimates were that 150,000-200,000 people could lose power if winds topple transmission towers.
At Cairns airport, people queued from dawn to catch the last flights out of the city before the terminal was locked down and sandbagged against potential storm surges.
Queensland, which accounts for about a fifth of Australia's economy and 90 percent of its steelmaking coal exports, has had a cruel summer, with floods sweeping across it and other eastern states in recent months, killing 35 people.
The state is also home to most of Australia's sugar industry and losses for the industry from Yasi could exceed A$500 million, including crop losses and damage to farming infrastructure, industry group Queensland Canegrowers said.