(Reuters) - Thousands of residents fled their homes and crammed into shelters in northeastern Australia as a cyclone described as the most powerful in the country's history and with a 650 km (400 mile) wide front barreled toward the coastline on Wednesday. "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 cities of Cairns, Townsville and Mackay. The entire stretch is popular with tourists and includes Australia's Great Barrier Reef.
Satellite images showed Yasi as a massive storm system covering an area bigger than Italy or New Zealand, with the cyclone predicted to be the strongest ever to hit Australia.
It is expected to hit the coast on Wednesday evening, packing winds of nearly 300 km (186 miles) per hour.
"All aspects of this cyclone are going to be terrifying and potentially very very damaging," Bligh said, adding the greatest threat to life could come from surges of water of up to four meters above normal high tide levels along the coast. The storm is due to hit when the tide is high.
Mines, rail lines and coal ports have all shut down, with officials warning the storm could drive inland for hundreds of kilometers, hitting rural and mining areas still struggling to recover after months of devastating floods.
Outside a shuttered night market in the tourist city of Cairns, nervous backpackers tried to flag down cars and reach temporary evacuation centers 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.
Various buildings in Cairns, including schools and malls, have been designated as shelters for those fleeing the storm, with some fast filling up and several already full, according to messages sent on Twitter to local media.
At a sprawling shopping center, hundreds of people streamed into a makeshift shelter carrying backpacks, blankets and food.
"We've only got a loaf of bread and a few other things, so we hope it doesn't last too long or we'll run out," said local woman Kirsty Munro as she tried to gather her three children aged two, four and eight in the crush of people.
Australia has strict building standards and Queensland suffers regular cyclones, but experts warned that many homes and buildings may not be able to withstand winds of this magnitude.
"The building regulations make things a lot better off at lower wind speeds but once you get to extreme cases you are in uncharted ground," said Robert Leicester, a researcher at the Australian Commonwealth Scientific and Industrial Research Organization, who has studied the impact of previous cyclones.
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 cyclone is 650 km off the coast of northeastern Australia and is expected to make landfall at 10 pm local time (7 a.m. EST) on the Queensland coast between Cairns and Innisfail. Its strength is on a par with Hurricane Katrina, which devastated New Orleans in 2005.
Some rain was starting to fall and winds were picking up in Cairns. The main streets were largely deserted. Shops were closed and windows taped to stop shards of flying glass.
At a coffee shop on the Cairns waterfront, Scott Warren covered windows with black plastic sheeting and sandbags from a pickup truck, trying to work out how high he would need to build the barrier to escape a possible surge of seawater.
"We get a heap of cyclones every year, but this one has got everyone's attention," Warren said. "We're hoping for the best, but expecting the worst to be honest."
POWER, MOBILE PHONES MAY GO DOWN
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.
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.
"Do not bother to pack bags. Just grab each other and get to a place of safety," she said.
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.
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.
"We're so relieved to be on," said Paul Davis, from Sydney, as he stood in the line with his partner Sylvia Leveridge and three-year-old daughter Ella.
Queensland, which accounts for about a fifth of Australia's
economy and 90 percent of steelmaking coal exports worth about A$20 billion ($20.2 billion) a year, has had a cruel summer, with floods sweeping the eastern seaboard 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 approaching the north-eastern state of Queensland could exceed A$500 million, including crop losses and damage to farming infrastructure, industry group Queensland Canegrowers said on Wednesday.
