China has been sifting rubble for survivors of the deadly quake which hit the remote Qinghai region as thousands spent a freezing night in the open.

Rescuers used bare hands and picks to search debris as night fell, with little heavy lifting equipment in the mountainous, mainly Tibetan area.

Officials say 589 people died and 10,000 were injured when the quake struck Yushu county early on Wednesday.

But the death toll is expected to rise and further aftershocks are feared.

Relief flights carrying medical workers and supplies have been landing in Yushu airport but the road to the town of 70,000 people has been blocked by a landslide, the Associated Press news agency reports from Qinghai's provincial capital, Xining.

The BBC's Chris Hogg, in Qinghai and travelling by road to the disaster area, passed long columns of military vehicles carrying diggers and other heavy lifting equipment as dawn was breaking on Thursday.

The columns, which included ambulances, were about eight or nine hours from the disaster zone, he said.

In the township of Jiegu, 85% of buildings were destroyed, officials say, and state TV has been showing street after street reduced to rubble.

Several schools collapsed and at least 56 students are known to have died, 22 of them in a school in Yushu.

Chinese President Hu Jintao has called for an all-out effort to save as many people as possible and some 5,000 rescuers, including 700 soldiers, have been sent to the disaster area.

The civil affairs ministry said it was to send 5,000 tents, 50,000 coats and 50,000 quilts as local officials in Yushu reported a lack of tents, medicines and medical equipment.

China has received messages of sympathy and offers of aid from foreign states including Japan, Russia and France.

'So much dust'

About 900 people have been pulled alive from under the rubble since the quake struck at 0749 on Wednesday (2349 GMT Tuesday), at the shallow depth of 10km (six miles), Chinese media say.

But Wu Yong, a local army commander, said the death toll could rise "as lots of houses collapsed".

Rescue operations were being hampered by the fact that the magnitude 6.9 quake disrupted telecommunications, knocked out electricity and triggered landslides.

In Xining, some 860km (530 miles) from the quake zone, soldiers, fire-fighters and rescue workers with sniffer dogs thronged the airport, which closed to civilian flights for several hours to make way for relief planes.

Efforts are being slowed down by the lack of jet fuel stored at Yushu airport. Relief planes are having to carry extra fuel, limiting their space for supplies.

As local officials struggled to find accommodation for the thousands of people left homeless, weather forecasters were predicting wind and sleet in the coming days, putting victims at risk of exposure.

Luo Song, a monk from a monastery in Yushu county, said his sister who worked at an orphanage there had told him three children were sent to a hospital but the facilities lacked equipment.

"She said the hospitals are facing a lot of difficulty right now because there are no doctors, they have only bandages, they can't give injections, they can't put people on intravenous drips," he told AP by phone from the southern Chinese city of Shenzhen.

In Jiegu, hotel manager Ren Yu said that nearly all of the local mud and wood houses had collapsed.

"There was so much dust in the air, we couldn't see anything," he said.

"There was a lot of panic. People were crying on the streets. Some of our staff, who were reunited with their parents, were also in tears."

Harrowing photographs have emerged of emergency workers removing dust-covered dead infants from rubble.

The high-altitude region is prone to earthquakes but, according to the US Geological Survey, this was the strongest tremor within 100km of the area since 1976.

In 2008, a huge quake struck neighbouring Sichuan province, about 800km from Yushu. That left 87,000 people dead or missing and five million homeless.