Smash hit

About 900 teenagers were buried under a collapsed three-storey school building. Wen Jiabao, the Chinese Premier, who flew to the region after the quake hit, bowed three times in grief before some of the first 50 bodies were pulled out.

"Not one minute can be wasted," said Mr Wen, a trained geologist. "One minute, one second could mean a child's life."

The China Seismological Bureau said that only 58 people had been extricated from demolished buildings across the quake area so far. In one county, 80 percent of the buildings had been destroyed.

"Survivors can hold on for some time. Now it’s not time to give up," said Wang Zhenyao, disaster relief division director at the Ministry of Civil Affairs in Beijing.

But while Mr Wang put the death toll at 11,921, Xinhua later said more than that had been killed in Sichuan alone. Apart from the 22,000 dead or trapped in Mianyang there were also at least 4,800 buried in debris in Mianzhu.

At a secondary school in Dujiangyan, more than 320 of the 420 pupils were crushed to death, reported Xinhua.

In another town, Beichuan, where 5,000 are feared dead, the old town had been almost completely buried by a landslide, residents said. In the new town, built on the banks of a river, the casualty toll was also expected to be high after the earthquake sent hundreds of buildings slipping into the water below.

The area has been hit by wave after wave of aftershocks, including a particularly violent tremor today measuring 6.1 that sent thousands of office workers in Chengdu rushing out into the open. Tens of thousands of people were already standing on the pavements huddling under umbrellas and makeshift plastic covers, sheltering from the rain, reluctant to return to their homes.

One said: "We are just too afraid that our homes will fall down."

Flights into Chengdu were delayed for hours to enable military relief planes to arrive. The airfield was scattered with military aircraft and hundreds of soldiers, mobilised to help with the rescue effort.

The few roads that lead to the mountainous centre of the earthquake area have been ordered to close so that any relief vehicles bringing aid and taking out the injured can move unimpeded. The railways ministry has declared a state of emergency on lines leading into Sichuan, and the health ministry has issued an urgent appeal for blood donors.

The foreign ministry said that it welcomed offers of international aid.

Local radio and television in Sichuan were broadcasting round-the-clock coverage of the disaster taking telephone calls from distraught relatives and passing on messages to loved ones out of contact at the heart of the quake.

The British Embassy in Beijing said it had sent four emergency workers to Chongqing to assess the situation of its nationals in the area.

The Association of British Travel Agents (Abta) said that it had been able to confirm the safety of 100 British tourists travelling in Sichuan in organised tours arranged by large holiday companies although it had spoken to only six of its 50 members who take tour groups to China.

An Abta spokeswoman said that reports from the Wolong reserve, which houses more than half of China's captive giant pandas, said that the endangered bears had survived the quake unscathed.

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