The 7.8-magnitude earthquake devastated a hilly region of small cities and towns in Sichuan and nearby provinces. The official Xinhua News Agency said 8,533 people died in Sichuan alone and dozens of other deaths were reported in surrounding areas.

Xinhua said 80 per cent of the buildings had collapsed in Sichuan province’s Beichuan county after the quake, raising fears the overall death toll could increase sharply.

State media said a chemical plant in Shifang city had cratered, burying hundreds of people and spilling more than 80 tons of toxic liquid ammonia from the site.

The earthquake sent thousands of people rushing out of buildings and into the streets hundreds of miles away in Beijing and Shanghai. The temblor was felt as far away as Vietnam and Thailand.

It posed a challenge to a government already grappling with discontent over high inflation and a widespread uprising among Tibetans in western China while trying to prepare for the Beijing Olympics this August.

The quake hit about 60 miles northwest of Chengdu — a city of 3.75 million — in the middle of the afternoon when classrooms and office towers were full. There were several smaller aftershocks, the US Geological Survey said on its Web site.

Xinhua said 50 bodies had been pulled from the debris of the school building in Juyuan town but did not say if the children were alive. Students also were buried under five other toppled schools in Deyang city, Xinhua reported.

Its reporters saw buried teenagers struggling to break loose from underneath the rubble of the three-story building in Juyuan “while others were crying out for help.” Two girls were quoted by Xinhua as saying they escaped because they had “run faster than others.”

Photos showed heavy cranes trying to remove rubble from the ruined school. Other photos posted on the Internet and found on the Chinese search engine Baidu showed arms and a torso sticking out of the rubble of the school as dozens of people worked to free them, using their hands to move concrete slabs.

Calls into the city did not go through as panicked residents quickly overloaded the telephone system and the quake also affected power networks.

Although it was difficult to telephone Chengdu, an Israeli student, Ronen Medzini, sent a text message to the Associated Press saying there were power and water outages there.

“Traffic jams, no running water, power outs, everyone sitting in the streets, patients evacuated from hospitals sitting outside and waiting,” he said.

The road to Wenchuan from Chendu was cut off by landslides, state media said, slowing the rescue efforts.

Though news trickled out in the first hours after the quake, the government and its media quickly mobilised, with nearly 8,000 soldiers and police sent to the area. China Central Television ran non-stop coverage, with phone reports from reporters and a few isolated camera shots from the scene.

Disasters always pose a test to the communist government, whose mandate in part rests on providing relief to those in need. In recent years, the government has improved emergency planning and rapid response training for the military.

The earthquake also rattled buildings in Beijing, some 930 miles to the north, less than three months before the Chinese capital was expected to be full of hundreds of thousands of foreign visitors for the Summer Olympics.

Li Jiulin, a top engineer on the 91,000-seat National Stadium — known as the Bird’s Nest and the jewel of the Olympics — was conducting an inspection at the venue when the quake occurred. He told reporters the building was designed to withstand a 8.0 quake.

“The Olympic venues were not affected by the earthquake,” said Sun Weide, a spokesman for the Beijing organising committee.

Other officials said the Three Gorges Dam was also unaffected.

Skyscrapers swayed in Shanghai and in the Taiwanese capital of Taipei.

Past Strikes

BEIJING:China’s worst earthquake was in July 1976, a 7.8 Richter temblor that killed at least 270,500 people in Tangshan. The other recent quakes are:

•May 12, 2008: An earthquake measuring 7.5 shakes China’s Sichuan province

•March 21, 2008: An earthquake measuring 7.2 hits the remote northwestern region of Xinjiang; damage was limited

•February 2003: At least 94 people are killed and more than 200 injured when a quake measuring 6.8 hits sparsely populated Jiashi county in

Xinjiang

•January 1998: At least 47 people are killed and more than 2,000 injured when an earthquake measuring 6.2 rocks Hebei, devastating mud and brick homes in two rural counties

•April 1997: A strong earthquake measuring 6.6 strikes Xinjiang, killing nine people and injuring 60.

•November 1988: Earthquake measuring 7.6 devastates remote areas in Yunnan, killing at least 730 people.