The government estimates the powerful quake has already killed some 50,000 people, and the chance of finding survivors buried in the rubble is diminishing by the hour.

Across the southwest province of Sichuan, teams of soldiers, volunteers and medics are clawing through mounds of shattered concrete that were once homes, schools and factories.

'Quake relief work has entered into the most crucial phase,' President Hu Jintao said after flying to Mianyang, one of the cities worst hit in Monday's 7.9-magnitude quake.

'The challenge is still severe, the task is still arduous and the time is pressing,' he said, quoted by China's state-run Xinhua news agency.

Strong aftershocks
A strong aftershock near the epicentre of China's devastating earthquake triggered landslides that cut off roads and buried vehicles, state media reported.

The aftershock, measuring 5.9 on the Richter scale, shook Lixian county, less than 50 kilometres from the epicentre of the quake, Xinhua news agency reported.

'A number of vehicles were buried in landslides triggered by the aftershock,' Xinhua said, citing its reporters on the scene.

State television reported separately that the aftershock also had cut off mobile telecommunication services that had just been restored in the area after being severed by Monday's earthquake, it said.

The aftershock 'added significantly to the difficulties' of carrying out relief work in Lixian county, the television station said.

China has mobilised tens of thousands of troops to handle the aftermath of the 7.9-magnitude quake, the country's worst in three decades.

Authorities estimate the earthquake had killed more than 50,000 people.

As of late Thursday, the affected region had experienced 122 aftershocks above four on the Richter scale, according to Chinese seismologists.

Child found alive after 80 hours

Rescuers on Friday pulled a child from the rubble of a collapsed school some 80 hours, state media said.

The child was found by rescuers searching the rubble of a school in the quake-devastated town of Beichuan, according to Xinhua.

The report said rescuers could hear more voices calling for help in the rubble and were 'expecting more miracles'. It did not specify the child's age or gender.

On Thursday, an 11-year-old girl was pulled from the rubble of another school in the badly hit town of Yingxiu.

Hopes fading

But officials have played down the chances of finding many more survivors, saying it would be miraculous for anyone to survive under the rubble for more than 72 hours.

And increasingly, rescuers have been dragging out bloodied bodies, bringing a new problem of disposal in communities that have almost nothing left.

Foreign rescue teams

After initially rebuffing offers of foreign aid teams, China has agreed to rescuers from Japan, Russia, Singapore and South Korea, and has issued a mass appeal for tens of thousands of shovels, hammers and cranes.

A Japanese team, the first to arrive, headed into a town where hundreds of families are reported buried, and a second Japanese team with sniffer dogs was en route.

South Korea is sending 44 experts and Singapore a team of 55 who helped in the aftermath of quakes in Indonesia, Pakistan and after the 2004 Indian Ocean tsunami.

They are bringing sniffer dogs, fibre-optic scopes, life detector systems and hydraulic cutters and spreaders.

Xinhua quoted a foreign ministry official saying it was the first time that China's government had accepted foreign professionals for a domestic disaster rescue and relief operation.

Death toll: 22,000
More than 22,000 people have been confirmed dead in China's Sichuan province from the earthquake, with another 14,000 people buried under rubble, a government official said on Friday.

Whole towns have been flattened, mountainsides sheared off, roads split in two, and countless thousands of buildings toppled or in danger of collapse.

The military, which has been spearheading rescue efforts, has scaled up its deployment, sending in extra transport planes, helicopters and troops.

They have been air-dropping tens of thousands of food packets, clothes and blankets, clearing roads, repairing bridges, sifting through the wreckage and ferrying the injured to hospital.

Rescue teams have also headed in from Taiwan - which China considers to be part of its territory - and Hong Kong.

Bai Licheng, a senior Communist Party official in Sichuan's Aba prefecture, warned of the risk of disease as bodies rot in the warmth.

'We are in urgent need of body bags,' he said in Yingxiu. 'Air-dropped food and drinking water are limited, and far from meeting the demand.'

Separately, the government was reported to be drawing up evacuation plans amid concerns that dams could collapse if rain persists.

The risk is especially acute in areas such as the counties of Wenchuan and Beichuan near the earthquake epicentre, state media said. - AFP