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 and it was not immediately known whether it had been affected.

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.

Rescue

Local government officials and soldiers in Yushu have been dispatched to save the buried people.

The Qinghai provincial government has sent a 62-member rescue team to the quake-hit region, a spokesman with the Qinghai Provincial Department of Civil Affairs said.

The department has also allocated 5,000 tents to the region, he said.

Meanwhile, the Ministry of Civil Affairs has allocated 5,000 tents, 50,000 cotton-padded clothes and 50,000 quilts to the region.

In addition, the Red Cross Society of China has dispatched a relief team to Yushu and allocated 100,000 yuan (US$14,706), 500 tents, 1,000 cotton-padded clothes and 1,000 quilts as relief supplies.

Pupils of some primary schools were among the buried, but the number was unknown, said Shi Huajie, an army police officer in the rescue operation.

"We have to mainly rely on our hands to clear away the debris as we have no large excavating machines," he said. "We have no medical equipment, either."

"Our soldiers have pulled 10 people from the collapsed houses, but four of them had died," said Wu Yong, commander of the Yushu Military Area Command of the Chinese People's Liberation Army.

"The death toll may rise further as lots of houses collapsed," he said.

"We are now putting up tents and transporting oxygen to prepare for treating the injured," he said.

"But roads leading to the airport have been damaged, hampering the rescue efforts," he said.

"In addition, frequent aftershocks and strong winds make the rescue operation more difficult," he added.

The quake struck the Yushu County in the Yushu prefecture at 7:49 AM with a depth of about 33 km. The epicenter is calculated to be 33.1 north and 96.7 east, the China Earthquake Networks Center reported.

At least 18 aftershocks have been reported so far, with the biggest being 6.3 magnitude about an hour and 36 minutes later.

"Aftershocks above 6 magnitude are still likely to happen in the coming several days," warned Liu Jie, of the China Earthquake Networks Center.

Earlier on 5:39 AM, a 4.7-magnitude jolted the county with a depth of about 6 km, the center reported.

Yushu is a quake-prone region.

(Xinhua News Agency April 14, 2010)