MANILA, Philippines -- Hours before Typhoon Haiyan hit, Philippine authorities moved 800,000 people to sturdy evacuation centres -- churches, schools and public buildings. But the brick-and-mortar structures were simply no match for the jet-force winds and massive walls of waves that swept ashore Friday, devastating cities, towns and villages and killing thousands, including many of those who had huddled in government shelters.

The tragedy is another reminder that nature's fury is sometimes so immense that it can overwhelm even the most diligent preparations. Combine that with a string of unfortunate circumstances -- some man-made -- and the result is the disaster of epic proportions that the country now faces.

"Sometimes, no matter how much and howcarefully you prepare, the disaster is just too big," saidZhang Qiang, an expert on disaster mitigation at Beijing Normal University's Institute for Social Development and Public Policy.

Some officials estimate that 10,000 or more people were killed by Haiyan, washed away by the churning waters that poured in from the Pacific or buried under mountains of trash and rubble. But it may be days or even weeks before the full extent of the destruction is known.

As dire forecasts poured in to predict a storm that would be among the most powerful on record, authorities prepared by evacuating people from flimsy homes along the coast to concrete structures farther inland.

Similar tactics had worked only weeks earlier when powerful Cyclone Phailin struck India's eastern shore, killing just 25 people as thousands more sheltered in government evacuation centres away from the sea. And Vietnam appeared to have successfully evacuated some 600,000 people before a weakened Haiyan arrived there early Monday.

But Philippine officials had not anticipated the 6-metre storm surges that swept through Tacloban, capital of the island province of Leyte, which saw the worst of Haiyan's damage. And while many perished in shelters, others ignored the evacuation and stayed put in their homes, either out of fear their property would fall prey to looters or because they underestimated the risk.

"I was talking to the people of Tacloban," said senior presidential aide Rene Alemendras. "They said 'we were ready for the wind. We were not ready for the water.'

"We tried our very best to warn everybody," he said. "But it was really just overwhelming, especially the storm surge."

While the storm surge proved deadly, much of the initial destruction was caused by winds blasting at 235 kilometres per hour that occasionally blew with speeds of up to 275 kph, howling like jet engines.

Lt. Col. Fermin Carangan, an air force commander in Leyte, said he was at his base in Tacloban, preparing for the storm with his men when the wind and water started coming in.

"It was 7:30 in the morning," he said. "The rain and wind were so strong and the water surged in fast and rose without letup. We had no time to move elsewhere, so we clambered up the room, about 10 of us.

"Then the roof started to peel off. One by one, we were exposed to the rain and we were just holding to the roof wooden beams. Then the walls of the building started collapsing and each one of us started falling into the water. We were yelling at each other. Then all of us got separated," said Carangan, 45.

The 25-year veteran of the air force managed to grab a wooden truss from the roof and clung to it for five hours while being buffeted by waves.

"The tide was coming from all over ... I had no sense of direction," he said. The waves eased after five hours and he paddled his makeshift lifeboat toward land in a neighbouring province. Gashed, cut and bruised, he hit a coconut tree and noticed a boy about 7-year-old floating nearby, clinging to a piece of wood.

Carangan got hold of the boy and made it to the nearby village. After handing over the boy to a policeman he limped 7 kilometres to an army outpost.

The Philippines, which sees about 20 typhoons per year, is cursed by its geography. On a string of some 7,000 islands, there are only so many places to evacuate people to, unless they can be flown or ferried to the mainland.

The Philippines' disaster preparation and relief capacities are also hampered by political factors. It lacks a strong central government and provincial governors have virtual autonomy in dealing with local problems.

Contrast this with Vietnam, which sees about a dozen typhoons per year and is similarly poor and densely populated. But a centralized, Communist Party-led government broadcasts clear messages that cannot be ignored by the provinces. Also, because of a clearly defined land mass, unlike the archipelago of the Philippines, it is easy to evacuate people deep inland and to higher ground.

"This is not the time to judge," said Alemendras, the presidential aide. "The national government and the local government all need to work together not to criticize anyone or not to show that one is better than the other."

But even with adequate resources and a robust government authority, forces of nature and the unpredictability of people can scuttle even the best advance planning. The 2011 tsunami in Japan might have killed many more without in-place emergency response measures, but an inadequate response to the nuclear crisis that followed seriously compounded the disaster.

Nor are such catastrophes limited to poor countries like the Philippines. When Hurricane Katrina plowed ashore near New Orleans in 2005, more than 1,400 were killed, many of whom ignored orders to evacuate before it hit.

Gwendolyn Pang, the executive director of the Philippine Red Cross, said Haiyan was three times more powerful than Katrina.

She said there should be an educational campaign to explain to people the destructiveness of a storm surge, which is like a tsunami.

"We should really start understanding this and make it our way of life, part of our readiness and preparedness," she added

Christopher Bodeen reported from Beijing. Associated Press reporters Jim Gomez in Tacloban and Teresa Cerojano in Manila contributed to this report.