Soldiers and civilians used shovels and their bare hands to dig through collapsed buildings in search of survivors after strong earthquakes struck a mountainous Tibetan region of China on Wednesday, killing at least 617 people and injuring more than 10,000.

The series of quakes flattened buildings across remote western Yushu county and sent survivors, many bleeding from their wounds, flooding into the streets of Jiegu township.

A series of earthquakes shook parts of Qinghai province in western China on Wednesday, killing at least 400 people. (CBC)State television showed block after devastated block of toppled mud and wood homes. Local officials said 85 per cent of the structures had been destroyed.

Residents and troops garrisoned in the town pulled survivors and bodies from the rubble much of the day. Several schools collapsed, with the state news agency saying at least 56 students died. Worst hit was the Yushu Vocational School, where Xinhua cited a local education official as saying 22 students died.

China National Radio said rescuers have pulled more than 2,000 survivors from the rubble in affected areas of Qinghai.

Footage on Qinghai Satellite TV showed bodies wrapped in blankets lying on the ground while rescuers pulled shards of concrete from a pancaked school building.

Crews set up emergency generators to restore operations at Yushu's airport, and by late afternoon the first of six flights landed carrying rescue workers and equipment. But the road to town was blocked by a landslide, hampering the rescue as temperatures dropped below freezing. Tens of thousands of the town's 70,000 people were without shelter and spent the night outdoors, state media said.

Houses crumble, people flee

The first quake hit Qinghai's Yushu county early Wednesday morning, forcing people into the streets. A 6.9-magnitude quake was the largest of six temblors recorded in the area in just three hours, the U.S. Geological Survey said.

Witnesses in the remote area near Tibet said houses quickly crumbled and the roofs of religious temples collapsed. Many hospitals were damaged and local media reports said some students may have been buried inside collapsed schools.

President Hu Jintao sent a vice-premier to supervise rescue efforts and more than 5,000 soldiers, medical workers and other rescuers were mobilized, joining 700 soldiers already on the ground, the official Chinese news agency said.

Rescue workers pull a person from a collapsed building in Yushu county in western China's Qinghai province Wednesday. (Associated Press)Yushu county is about 800 kilometres southwest of the provincial capital Xining and has a population of about 100,000, mostly herders and farmers.

Emergency crews are still trying to assess the damage from the earthquakes, but an emergency official was quoted as saying the number of injured had risen to more than 10,000.

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."

Foreign Affairs Minister Lawrence Cannon says there are no reports of any Canadian deaths or injuries.

Offering Canada's condolences to the people of China, Cannon said Ottawa was deeply concerned for the well-being of all those affected by the disaster.

The government of China has not requested international assistance, he said.

Mei Mei Leung, a staff member with World Vision in Beijing, said she thinks it will take her team at least two days to reach the affected area, as local roads were badly damaged in the quakes.

Crews are already trying to clear the rubble and repair damaged roads so emergency crews and equipment can be moved into the area.

Chinese officials are airlifting some supplies into affected communities and have promised to send at least 5,000 tents and 100,000 coats and blankets into the region to provide emergency aid to people who lost their homes.

Most residents' houses are of quite poor quality, so 90 per cent of them were destroyed," said Gu Guohua, an earthquake expert with China's seismological bureau.

"Nearly all the houses made of mud and wood collapsed. There was so much dust in the air, we couldn't see anything," said Ren Yu, general manager of Yushu Hotel in Jiegu, the county's main town.

The hotel was not badly damaged, but staff moved more than 100 guests out of the hotel into open public spaces, Ren told The Associated Press by phone.

After transporting guests to safety, hotel staff then helped rescue efforts in other buildings, Ren said.

"We pulled out 70 people, but some of them died on the way to the hospital," Ren said, adding other survivors were put in tents in the hotel yard while awaiting assistance.

The area is sparsely populated, unlike the more densely populated Sichuan province, where a deadly 2008 earthquake left almost 90,000 people dead or missing. The Sichuan quake flattened several schools, killing thousands of students. Poor design, shoddy construction and the lax enforcement of building codes were found to be widespread.

With files from The Associated Press, The Canadian Press