|Thousands of people have taken cover at evacuation centres as the 'monumental storm' approaches [REUTERS]
Tens of thousands have been evacuated in Queensland state, northeastern Australia, as a cyclone described as the most powerful in the country's history has barrelled toward the coastline.
Reports have suggested the storm has just hit the Australian coast, in the early hours of Thursday morning local time.
Police have been forced to turn people away from some shelters after they reached full capacity, and engineers warned that even "cyclone proof" homes could be blown apart by winds expected to reach 300km (186 miles) per hour.
"We are facing a storm of catastrophic proportions," Queensland state premier Anna Bligh said after Cyclone Yasi was upgraded to a maximum-strength category five storm.
More than 400,000 people live in the cyclone's expected path, which includes the popular tourist cities of Cairns, Townsville and Mackay.
The area is also the gateway to Australia's Great Barrier Reef.
Reporting from Cairns, Al Jazeera's Andrew Thomas said this was a cyclone-prone area, "but nothing on this scale," he said, calling Yasi a "monumental storm".
Satellite images showed Yasi covering an area bigger than Italy or New Zealand, and predicted to be the strongest ever to hit Australia.
Thomas reported weather bureau estimates which expected Yasi to peak at 10pm local time (1200GMT), making the four hours on either side of the peak "the real danger spots," he said.
The timing, just after high tide, also meant high storm surges of at least 6.5 feet (two metres) were likely to flood significant areas along the coast.
"This impact is likely to be more life-threatening than any experienced during recent generations," the Bureau of Meteorology said.
"What it all adds up to is a very frightening time," state premier Bligh said. "We're looking at 24 hours of quite terrifying winds, torrential rain, likely loss of electricity and mobile phones. People really need to be preparing mentally if nothing else."
Outside a shuttered night market in the tourist city of Cairns, nervous backpackers tried to flag down cars and reach temporary evacuation centres at a nearby university.
"We are terrified. We have had almost no information and have never seen storms like this," said Marlim Flagar, 20, from Sweden.
The Cairns airport closed on Wednesday after extra morning flights left. Tourists had fled beach resorts ranging from backpacker hostels to exclusive clubs.
Al Jazeera's Thomas reported that there were tourists stranded with nowhere else to go, whose only option was to hunker down at shelters with local residents.
Struggling with a surge of people arriving at the university evacuation centre, police later blocked more people from entering.
About 9,500 people had taken cover at evacuation centres by Wednesday afternoon, State premier Bligh said.
At a local shopping centre, hundreds of people had streamed into a makeshift shelter carrying backpacks, blankets and food.
The Queensland state premier said current estimates were that 150,000-200,000 people could lose power if winds topple transmission towers.
She also said that those in low-lying areas facing a risk of flooding from storm surges had "a window of opportunity" of a matter of hours to leave.
In Townsville alone, the storm surge could flood up to 30,000 homes, according to the town's web site.
The military has been helping to evacuate nearly 40,000 people from low-lying coastal areas, and also from the two major hospitals in Cairns.
Australia's huge, sparsely populated tropical north is battered each year by about six cyclones, called typhoons, throughout much of Asia and hurricanes in the Western hemisphere.