Many schoolchildren were buried as they were taking an afternoon nap. One body of a boy was found clutching a pen.

The official death toll climbed to 14,866, as rescuers pulled at tangled chunks of buildings for signs of life.

The government sent 50,000 troops to dig for victims and 90 more miliary and civilian helicopters were ordered to the region on Wednesday.

A paramilitary officer who arrived at Wenchuan, at the epicentre, told Sichuan TV a third of houses there had been destroyed and more than 90 percent damaged.

Amid the overwhelming gloom, there were also moments of joy. In Mianzhu, where thousands have already been confirmed dead, about 500 people were pulled out alive from crushed buildings.

Rescuers in Hanwang, a village in Mianzhu, sustained a girl with food and water as they struggled to free her from the ruins of a school.

A woman eight-months pregnant and her mother, trapped under an apartment building in Dujiangyan, were freed by firefighters.

"We are very happy. We have been standing here shouting for two days," said Pan Jianjun, a relative. "But there are still three more people in there making sounds."

But television showed whole villages wiped out across the poor, mountainous region suggesting searchers would find many more bodies than survivors among the toppled buildings.

BLOCKED RIVERS, DAMAGED DAMS

Officials have also warned of dangers from increased strain on local dams as well as mudslides on brittle hillsides where rain has been forecast over the next few days.

Two hydropower stations in Maoxian county, where 7,000 residents and tourists remain stranded near the epicentre, were "seriously damaged". Authorities warned that dams could burst.

Landslides had blocked the flow of two rivers in northern Qingchuan county, forming a huge lake in a region where 1,000 have already died and 700 are buried, Xinhua said.

"The rising water could cause the mountains to collapse. We desperately need geological experts to carry out tests and fix a rescue plan," Xinhua quoted Li Hao, the county's Communist Party chief, as saying.

The quake had also stopped a river in the stricken Mianzhu region, prompting officials to evacuate residents and drain dams downstream, the agency said.

Underscoring the urgency of relief efforts, the Communist Party's top discipline watchdog vowed to punish officials for any dereliction of duty.

Pictures from Beichuan, which rescuers have struggled to reach, showed near total devastation. Survivors lay alongside the dead in the open air, surrounded by rubble as state TV showed dramatic footage of soldiers parachuting in to help.

More than 3,000 domestic and foreign tourists stranded in Jiuzhaigou, a famous scenic spot in Sichuan Province, were evacuated to safety, said the National Tourism Administration, according to Xinhua.

PREMIER'S APPEAL

Premier Wen Jiabao made emotional appeals to workers and comfort orphaned children.

"Your pain is our pain," he said, standing amid a cluster of residents, some of whom wiped away tears. "Saving people's lives is the most important task."

The quake, the worst to hit China since 1976 when up to 300,000 died, has drowned out upbeat government propaganda three months ahead of the Beijing Olympic Games.

It has also muffled criticism from abroad over recent unrest in Tibet, with images of the human tragedy and heroic rescue efforts spurring offers of aid and an outpouring of sympathy.

The Party's swift action to mobilise a massive rescue force has made a jarring comparison with that of Myanmar, whose government's slow response to a devastating cyclone has infuriated aid and rights groups.

China's stock market initially weakened after the quake, partly on fears it could add to inflation that is already at a 12-year high, but the Shanghai stock index ended 2.7 percent higher as fears of the long-term impact ebbed.

Industrial production growth showed China's busy factories moving down a gear and economists said output growth could fade in coming months, partly due to the impact of the Sichuan quake.

Leading disaster-modelling firm AIR Worldwide said the cost of the quake was likely to exceed $20 billion.