• This screengrab taken from state CCTV shows Chinese military searching through the rubble of collapsed buildings in Yushu County. Picture: AFP/Getty Images
Thousands more were injured in the quake, centred on Yushu county, which has a population of about 100,000 mostly herders and farmers.
Police were forced to use shovels to dig through the rubble in one township where most of the homes had been flattened.
With most of the roads leading to the nearest airport damaged, equipment and rescuers were having problems reaching the area.
Downed phone lines, strong winds and frequent aftershocks also hindered rescue efforts.
Workers were racing to release water from a reservoir in the disaster area where a crack had formed after the quake.
The magnitude-6.9 quake struck in an area in the south of Qinghai province, near Tibet, the US Geological Survey said.
The USGS recorded six shocks in less than three hours, all but one registered 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 that appeared to be one of the worst hit, 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, according to CCTV. It did not say what type of school it was.
More than 85% of houses had collapsed in Jiegu, while large cracks have appeared on buildings still standing, the official Xinhua News Agency said.
The provincial emergency office said 700 soldiers were trying to clear the rubble and rescue buried people and that 1,000 more troops would be dispatched.
Local military official Shi Huajie said rescuers were working with limited equipment.
"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," Shi said. "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 temperatures of around 6C.
The epicentre of the first quake was 235 miles south-south-east of Golmud, a large city in Qinghai, at a depth of six miles, the USGS said.