The most powerful earthquake to hit China in 30 years has killed at least 10,000 people in south-western Sichuan province, with many more still trapped.  In one county alone, 80% of buildings collapsed, and up to 5,000 people died.

Officials say there is no news yet from the towns at the epicentre, which have a total population of more than 24,000.

President Hu Jintao has urged “all-out” efforts to rescue victims, and has ordered troops to help with disaster relief work.

The 7.8 magnitude quake struck on Monday, at 1428 local time (0628 GMT).

The number of dead is expected to rise once contact is made with Wenchuan county, which was at the epicentre of the shock.

Telephone lines to the area are down, and roads are blocked by fallen rocks and boulders.

The BBC’s Michael Bristow, in nearby Chongqing, said torrential rains have also prevented helicopters gaining access.

A top official from Wenchuan, Wang Bin, appealed via satellite phone for outside help.

“We are in urgent need of tents, food, medicine and satellite communications equipment through air drop,” he said.

“We also need medical workers to save the injured people here.”

Mr Wang was also quoted by the state news agency, Xinhua, as saying that farmers’ houses in two of the towns had collapsed, and 30,000 people in the county’s main town were staying outdoors, afraid to go home.

Rescue forces are approaching the area on foot.

Cries for help

There were also harrowing reports from the scene of a school collapse in Dujiangyan city – south-east of the epicentre – where 900 students were buried and at least 50 dead.

Teenagers buried beneath the rubble of the three-storey Juyuan Middle School building struggled to break free, while others were cried out for help, Xinhua reported.

Chinese Premier Wen Jiabao, who rushed to the scene, bowed three times in grief before some of the bodies that were pulled out, according to Xinhua.

“Not one minute can be wasted,” Mr Wen is quoted as saying. “One minute, one second could mean a child’s life.”

At another school in Dujiangyan, fewer than 100 students out of 420 are reported to have survived after their building collapsed.

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Devastation in China

Another of the worst-hit areas appears to be Beichuan county, about 50km from the epicentre.

Some 80% of buildings there were reported to have been destroyed, leaving between 3,000 and 5,000 people dead and up to 10,000 injured.

We were in quite a narrow street where everything just started shaking… people were panicking… It was mayhem Casper Oppenhuisdejong BBC reader in Chengdu

Meanwhile hundreds of people were reported to have been buried in two collapsed chemical plants in Shifang in Sichuan, and at least five other schools were reported to be in ruins.

More than 150 people were killed in the other provinces of Gansu and Shaanxi, and in Chongqing municipality, Xinhua said.

US President George W Bush expressed condolences to victims’ families, while Japan offered to send aid.

“The Chinese government are to be commended for their quick and efficient response. The UK stands ready to assist,” said British Foreign Secretary David Miliband.

Dozens of aftershocks have been reported since the quake, which was felt in Beijing, and the Thai capital Bangkok.

The earthquake was China’s worst since 242,000 people were killed in 1976 by the Tangshan quake.

Sichuan province is the most populated part of China – home to 87 million people.

RECENT CHINA QUAKES March, 2008: 7.2 quake in Xinjiang – damage limited February 2003: 6.8 quake in Xinjiang – at least 94 dead, 200 hurt January 1998: 6.2 quake in rural Hebei – at least 47 dead, 2,000 hurt April 1997: 6.6 quake hits Xinjiang – 9 dead, 60 hurt January 1997: 6.4 quake in Xinjiang – 50 dead, 40 hurt

The BBC’s Quentin Somerville says this is probably the most significant natural disaster to hit China in recent memory, but that the Chinese army has a good record of mobilising and getting people to safety.

He also says it is one of the most open and speedy responses to an emergency he has ever seen from Chinese state media.

The fact the quake was felt in Beijing, he says, means millions of people will feel connected to the disaster and will be watching TV screens closely to see how the government responds..