The U.S. Geological Survey reported on its Web site that a magnitude 6.9 temblor struck an area in southern Qinghai, near Tibet, on Wednesday morning and was followed by three quakes in the same area.
The main quake sent residents fleeing as it toppled houses made of mud and wood, said Karsum Nyima, the Yushu county television station's deputy head of news, speaking by phone with broadcaster CCTV.
"In a flash, the houses went down. It was a terrible earthquake," he said. "In a small park, there is a Buddhist tower and the top of the tower fell off.
"Everybody is out on the streets, standing in front of their houses, trying to find their family members," he said, adding that school buildings had not collapsed but that students had been evacuated and were assembled in outdoor playgrounds.
The quake hit the county of Yushu, a Tibetan area in Qinghai's south, the official Xinhua News Agency cited the China Earthquake Networks Center as saying. The Chinese center measured the quake's magnitude at 7.1. A local government Web site put the county's population in 2005 at 89,300, a community of mostly herders and farmers.
The China Earthquake Administration announced the initial death toll in a brief statement on its Web site. Rescue efforts were hindered by telecommunications problems, with phone lines down, the notice said.
State television showed footage of paramilitary police using shovels to dig around a house with a collapsed wooden roof. A local military official, Shi Huajie, told state broadcaster CCTV 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 labor," Shi said. "It is very difficult to save people with our bare hands."
Wu Yong, a local military chief, said medical workers were also urgently needed but that roads leading to the airport had been badly damaged by the quake, creating difficulties for people and supplies to be flown in.
The epicenter of the first quake was located 235 miles south-southeast of Golmud, a large city in Qinghai, at a depth of six miles, the USGS said.
Ten minutes later, the area was hit by a magnitude 5.3 quake, which was followed after two minutes by a temblor measuring 5.2, according to the U.S. agency. Both the subsequent earthquakes were measured at a depth of 6 miles (10 kilometers). Another quake, measuring 5.8, was recorded at 9:25 a.m.
CCTV cited Sun Shihong, an analyst at the China Earthquake Networks Center, as saying the subsequent temblors were aftershocks and that Yushu county is located in an earthquake-prone area.
Calls to the local Communist Party office and the government of Yushu county and the Qinghai provincial seismological bureau rang unanswered.
In 2008, a magnitude-7.9 quake in Sichuan province left almost 90,000 people dead or missing.