BEIJING — A series of strong earthquakes struck a mountainous Tibetan area of western China today, killing at least 400 people and injuring more than 10,000 as houses made of mud and wood collapsed, officials said. Many more people were trapped and the toll was expected to rise.

The largest quake was recorded by the U.S. Geological Survey as magnitude 6.9. In the aftermath, panicked people, many bleeding from their wounds, flooded the streets of a Qinghai province township where most of the homes had been flattened. Students were reportedly buried inside several damaged schools.

Paramilitary police used shovels to dig through the rubble in the town, footage on state television showed. Officials said excavators were not available and with most of the roads leading to the nearest airport damaged, equipment and rescuers would have a hard time reaching the area. Hospitals were overwhelmed, many lacking even the most basic supplies, and doctors were in short supply.

Downed phone lines, strong winds and frequent aftershocks also hindered rescue efforts, said Wu Yong, commander of the local army garrison, who said the death toll "may rise further as lots of houses collapsed."

With many people forced outside, the provincial government said it was rushing 5,000 tents and 100,000 coats and blankets to the mountainous region, at around 13,000 feet high and where night temperatures plunge below freezing.

Workers were racing to release water from a reservoir in the disaster area where a crack had formed after the quake to prevent a flood, according to the China Earthquake Administration.

The quake was centered on Yushu county, in the southern part of Qinghai, near Tibet, with a population of about 100,000, mostly herders and farmers.

The USGS recorded six temblors in less than three hours, all but one registering 5.0 or higher. The China Earthquake Networks Center measured the largest quake's magnitude at 7.1. Qinghai averages more than five earthquakes a year of at least magnitude 5.0, according to the official Xinhua News Agency. They normally do not cause much damage in the sparsely populated province.

Residents fled as the ground shook, toppling houses made of mud and wood, as well as temples, gas stations, electric poles and the top of a Buddhist pagoda in a park, witnesses and state media said. The quake also triggered landslides, Xinhua said.

The death toll rose to about 400, according to China Central Television. Emergency official Pubucairen, who goes by only one name, was quoted as saying that the number of injured has risen to more than 10,000. The official said rescuers were treating the injured at hospitals, race tracks and sports stadiums.