Powerful quake kills at least 400 in China

Thousands more were injured in the quake, centred on Yushu county,

which has a population of about 100,000 mostly herders and farmers.

Most of the roads leading to the nearest airport were damaged, preventing equipment and rescuers reaching the area, and forcing

police had to dig through the rubble with shovels.

Downed phone lines, strong winds and frequent aftershocks also hindered rescue efforts.

Workers were racing to release water from a reservoir where a crack has formed .

The magnitude-6.9 quake struck in an area in the south of Qinghai province, near Tibet. There were six shocks in less than three hours, all but one registering 5.0 or higher.

The main quake sent residents fleeing as it toppled houses made of mud and wood.

Local journalist Karsum Nyima said: "In a flash, the houses went down. It was a terrible earthquake.

"In a small park, there is a Buddhist pagoda and the top of the pagoda fell off. ... Everybody is out on the streets, standing in front of their houses, trying to find their family members."

The earthquake comes a little less than two years after a magnitude-7.9 quake in neighbouring Sichuan province left almost 90,000 people dead or missing.

That quake flattened several schools, killing thousands of students. Poor design, shoddy construction and the lax enforcement of building codes were found to be rampant.

In Jiegu, a township 20 miles from the epicentre, the local fire brigade was trying to rescue 20 students stuck inside a school.

They were also working to pull out 40 to 50 people trapped in a toppled four-story building.

More than 85 per cent of houses had collapsed in Jiegu, while large cracks have appeared on buildings still standing.

The provincial emergency office said 700 soldiers were trying to clear the rubble and rescue buried people. Local military officials said rescuers were working with limited equipment.

A spokesman said: "The difficulty we face is that we don't have any excavators. Many of the people have been buried and our soldiers are trying to pull them out with human labour. It is very difficult to save people with our bare hands."

Five thousand tents and 100,000 thick, cotton coats and heavy blankets were being sent to help survivors cope with strong winds and low temperatures.

President Hu Jintao has sent a vice premier to supervise rescue efforts and more than 5,000 soldiers, medical workers and other rescuers were mobilised.

A message of sympathy also came from the Dalai Lama, the exiled

spiritual leader of the Buddhist Tibetans.

The Yushu district has a large number of Buddhist residents who were caught up in the anti-government protests that swept Tibet in 2008.