Part of a vocational school had also collapsed and "a lot of students are buried underneath", he added.
Karsum Nyima, the Yushu county television station's deputy head of news, told state broadcaster CCTV that the main tremor sent residents fleeing as it toppled houses made of mud and wood.
"In a flash, the houses went down. It was a terrible earthquake," he said.
Divya Gopalan, Al Jazeera's correspondent in the capital Beijng, said the situation was bleak.
"Most of the buildings in the main township near the epicentre were damaged but we are hearing that those still standing have huge cracks, so people are worried they too could collapse," she said.
"We have been told that army trucks are being sent but that could take a very long time because the epicentre is far from the region's capital, as well as the problem of collapsed infrastructure - so it could take about 24 hours.
"Rescue workers tell us people are wandering the streets in a panic looking for medical aid, many people are trying to dig people, family and friends, out of the rubble with their bare hands because there is very little equipment."
The local administration said there was extensive damage to local structures, hindering rescue efforts.
"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 Huajie, a local military official, told CCTV.
"It is very difficult to save people with our bare hands."
Al Jazeera's correspondent said that another "devastating" factor in the aftermath of the quake was that a nearby reservoir had developed huge cracks.
"Authorities say rescue workers are trying to divert that water as quickly as possible because it could end up flooding areas that are populated," Gopalan said.
Qing Hui Gu, regional disaster management coordinator for East Asia with the International Federation of the Red Cross, said he expects the number of deaths and injured to rise in the coming days.
"Many relief teams from the government and the Red Cross already on their way to Yushu county should be reaching the town soon," he told Al Jazeera.
"In fact the military and volunteers are already at the scene offering assistance."
The Qinghai provincial government said in a statement that 5,000 tents and 100,000 thick, cotton coats and heavy blankets were being sent to help survivors cope with strong winds and near-freezing temperatures.
|State media said some 8,000 people have been injured in the quake [Reuters]
Wu Yong, a local military chief, said medical workers also were urgently needed but that roads leading to the airport had been badly damaged by the quake, creating problems for any aid effort.
He said rescue efforts were hindered by frequent aftershocks and strong winds.
The quake struck at 7:49am (23:49 GMT on Tuesday) and was centred in the mountains that divide Qinghai province from the Tibet Autonomous Region, 380km south-southeast of the city of Golmud.
The Xinhua news agency cited officials at the China Earthquake Networks Center as saying that at least 18 aftershocks have been recorded, with more and stronger tremors likely to occur in the coming days.