Special Report:7.1-magnitude quake hits Qinghai>>

Thousands of rescuers battled strong winds and altitude sickness amid aftershocks to reach survivors Thursday, one day after a 7.1-magnitude quake killed 617 and injured 9,110.

Premier Wen Jiabao, who visited Yushu Prefecture Hospital in Qinghai province on Thursday, holds the hand of a Tibetan woman injured in the quake. Vice- Premier Hui Liangyu (center) accompanied Wen on the trip.

The strongest and deadliest tremor in almost two years also left 313 missing, mostly in Yushu prefecture of Qinghai.

More than 15,000 residential buildings - or 85 percent of all homes, mostly mud-and-wood structures - have been flattened, and 100,000 people have been made homeless, according to the rescue headquarters.

As rescuers raced to transport tents, quilts and other relief materials to the region, many survivors in hardest-hit Gyegu town, the seat of the Yushu prefecture government and home to 100,000 people, spent Wednesday night in the freezing open air.

To help direct relief efforts, President Hu Jintao decided to cut short his South America visit and headed home after attending the BRIC summit in Brazil.

"At this difficult time, I need to return to China as soon as possible and join the people in disaster relief," Hu told leaders of Venezuela and Chile over the phone. He was scheduled to visit the two countries from Saturday to Monday.

Premier Wen Jiabao, who decided to postpone his visit to Brunei, Indonesia, and Myanmar next week, rushed to the region Thursday evening to supervise rescue operations, which are headed by Vice-Premier Hui Liangyu.

Many were still trapped under the debris in the region, where resources have become scarcer even as people and supplies poured in by road and air.

Civil affairs officials on Thursday said they hoped to transport 10,000 tents, or nearly a quarter of the planned total, to the region by the end of the day.

A stadium and the town square in Gyegu offered shelter for residents Thursday.

Tsering, 44, was camped with his wife and four children on a lawn, where more than 300 people sought temporary refuge near the town's armed police headquarters in the absence of shelters.

"It's so cold at night. We need tents and food as soon as possible," he told China Daily. A half bag of flour he pulled from the debris was all the food his family had.

Rescuers pull Zou Jiang, owner of a photo studio, from a collapsed building in Gyegu, Yushu, on Thursday.

Drolma, 50, managed to pull her youngest daughter out from the debris after a quake-incurred landslide buried her house. But the girl could not receive any treatment as local hospitals were not operational and medics from outside were overwhelmed.

Many injured were rushed Thursday to hospitals in Xining, the provincial capital 800 km away, by buses, privately-owned cars and planes. But on the highway linking Yushu and Xining, sandstorms reduced the visibility to only about 100 meters in some sections, which hampered rescue efforts.

In Gyegu, many residents began to search for food and blankets in the debris while rescuers, tired from the high winds and thin oxygen, continued to pull survivors and bodies from street corners and flattened buildings.

Residents crowded around gas stations, eager to fill up their motorbikes, the major means of transport in Gyegu.

Xie Jiaxin, political commissar of an armed police unit that arrived at the town at 6 pm on Wednesday, told China Daily that finding survivors remained the team's top mission.

The death toll, he said, could rise. "The tremor hit in the early morning when many locals were still sleeping," said Xie, who also joined rescue operations after the Wenchuan earthquake on May 12, 2008.

In addition to professional search and rescue teams, almost 2,000 soldiers, police officers and firefighters were using excavators, shovels or even bare hands to comb through the debris for survivors. Tibetan monks dressed in maroon robes, too, joined residents and rescuers to search for people buried in the debris in Gyegu.

As Yushu is a community of predominantly ethnic Tibetans, almost 100 college students fluent in Tibetan volunteered to help out at hospitals in Xining, where many survivors were receiving treatment.

"Only a few doctors here speak Tibetan. So I put up a post online on Wednesday, both on Baidu and my QQ blog," Yang Jing, an organizer of the students, told China Daily.

According to him, the students who turned up for help were dispatched to almost every big hospital in Xining. At the Qinghai People's hospital, where Yang was working, 100 victims were receiving treatment as of 6 pm Thursday, its director Xi Aiqi said.