How China's Red Army took just 20 minutes to swing into action after devastating earthquake

Within hours, Premier Wen Jiabao was on a plane to the disaster zone in Sichuan province to direct the relief effort.

Within a day, roads leading to towns and villages toppled by the quake were starting to clog up with cars, trucks and buses carrying water, food, tents and volunteers eager to pitch in.

Assistance: Soldiers control a crowd waiting to be evacuated by bus out of the earthquake-hit city of Wenchuan

China's initial response to its worst natural disaster in a generation was fast, large and unprecedented.

It was in stark contrast to the Myanmar junta's slow, opaque efforts after this month's deadly cyclone and the U.S. government's much-criticised reaction to Hurricane Katrina.

"I think it is not an exaggeration to say that this is probably the most swift and effective response to a large-scale natural disaster in peacetime by any government in history," said Wenran Jiang, a political scientist at the University of Alberta.

Francis Markus, of the International Federation of Red Cross and Red Crescent Societies, said the response was "exemplary".

Emergency: Military helicopters lift off to evacuate the earthquake evacuees from the quake-strucken Wenchuan county

The central leadership's ability to sense the scale of the disaster and launch major rescue work almost at once has won it unprecedented support and sympathy, analysts say.

But that goodwill will be tested by huge challenges in the days and weeks to come, as authorities struggle to provide proper food and shelter for the 5 million homeless, stave off epidemics and conduct satisfactory investigations into quake-related scandals, such as the high number of schools that collapsed.

The task is pressing for a stability-obsessed authoritarian government, which hosts the Olympic Games in August and is counting on presenting a smiling face to the world.

Disaster: A man pushes his bicycle on a street, which was affected by a mudslide, in the earthquake-shaken city of Wenchuan

The huge quake-related problems have added to the raft of challenges with which the Communist Party was already grappling on a daily basis -- soaring inflation, environmental degradation and economic growth. Always uppermost in leaders' minds is the need to avert public disorder.

Qian Gang, a former journalist who wrote a book about the 1976 Tangshan earthquake in northern China which killed up to 300,000, said preventing disease and mitigating the risk of floods from lakes formed by landslides should be top priorities.

In the quake zone, many victims grumbled about inadequacies and shortcomings.

A stadium where refugees were sheltering was overcrowded, and many elsewhere were still living in makeshift tents. Villagers gathered on rural roadsides, some holding signs saying they desperately needed food and water.

In the town of Yinhua, refugees longed for tents and some change to a diet consisting almost solely of instant noodles.

Rescue mission: A worker walks in between temporary housing being built for residents affected by an earthquake in Dujiangyan

A teacher from a middle school in Beichuan that collapsed, killing hundreds, admitted that the army had arrived quickly but said they were initially ineffective.

"Not much got done until Wen Jiabao came here," said the man who declined to give his name. Wen visited Beichuan two days after the quake.

"The army got there and didn't do anything. They didn't have any of the proper tools. Only the local people did anything to try to save people. Eventually, only a small amount of soldiers went in, but they were useless."

Others complained that it took three days for the government to start to admit experienced rescue teams from Japan, Russia, Taiwan, South Korea and Singapore. Only the Russians have rescued a survivor from the rubble.

The magnitude 7.9 quake left more than 51,000 people dead and more than 20,000 missing, and injured a further 247,000.

New hope: Temporary housing built for residents affected by an earthquake is seen in Dujiangyan

In the township of Wufu and in at least one other area where a school collapsed, angry parents of dead pupils accused low-level officials of corruption and sought retribution.

Information about the quake has flowed almost unfettered after thousands of journalists ignored the Party propaganda department's orders not to go to the scene.

As long as the news remains upbeat, they will be allowed to continue for a while, said one journalist who was heading to the quake area, but eventually the censors would tighten their grip.

"The next few months of work for the Chinese government will be extremely difficult," said Shi Yinhong, a politics expert at Beijing's Renmin University.

"This is definitely a challenge for the Chinese government."