"I can see injured people everywhere. The biggest problem now is that we lack tents, we lack medical equipment, medicine and medical workers," he said.

The epicenter is at the Rima Village in the Shanglaxiu Township, about 50 km west of Gyegu and about 800 km away from Xining, the Qinghai provincial capital.

"The epicenter is a pasturing area and sparsely-populated. I think the quake would not cause casualties as heavy as those in Jiegu," Zhuohuaxia said.

Zhu Liang, a driver at the Yushu prefecture government, said he saw half of the buildings in the Yushu Vocational School had collapsed.

"I do not know how many students have died," said Zhu, who is now in the rescue operation.

"Students just got up and were yet to go to class when the quake happened. I recovered several bodies from the debris and found they were fully dressed," he said.

"Buildings in our school were all toppled, and five pupils have died," said a teacher surnamed Chang at the Yushu Primary School, a boarding school with about 1,000 students.

"Morning sessions did not begin when the quake happened. Some pupils ran out of dorms alive, and those who had not escaped in time were buried," Chang said.

"The houses here are almost all made of wood and earthen walls, which will easily collapse when a quake happens," said Karsum Nyima, deputy director of the News Department of the Yushu TV Station.

Although Yushu is a sparsely-populated region, experts said the quake is very likely to cause "heavy" casualties.

"The strong quake has a shallow depth and the epicenter is close to the prefecture seat," said Sun Shihong, a research fellow with the China Earthquake Networks Center in Beijing.

"It is estimated there will be heavy casualties, as the quake occurred in the early morning and most of the local residents were yet to get up," he said.

"In addition, according to the building structure and damages, a large number of people will be injured," he added.

The quake led to a temporary cut of telecommunications and damaged roads to the airport. The epicenter is about 200 km away from the Qinghai-Tibet Railway.

"The railway line does not go through Yushu, so it is unlikely to be affected by the quake," said Lin Zhigang, of the Qinghai-Tibet Railway Company.

The quake was strongly felt in the neighboring Qamdo Prefecture and other regions in Tibet.

"But no casualties or major damages have been reported so far. We are investigating the losses," said Zhu Quan, director of the Tibet Autonomous Regional Seismological Bureau.

The bureau has dispatched an emergency team made up of 63 professional rescuers to Yushu, Zhu said.

"They left Qamdo in the morning and will arrive at Yushu in the afternoon," he said.

Another 17 rescuers have set off for Yushu from the Tibet regional capital of Lhasa, and they are expected to arrive at the region Thursday, he added.

The quake was also felt in parts of the neighboring Tibetan Autonomous Prefecture of Garze in Sichuan Province.

"In addition to five deaths, some houses were damaged or toppled, and some highways were disrupted," said Guo Jin, director of the Garze Bureau of Earthquake and Disaster Relief.