A series of aftershocks have since hit the provincial capital, Chengdu
The Chinese authorities have launched a major rescue operation in Sichuan province, after it was struck by the most powerful earthquake to hit the south-west of the country in 30 years.
More than 8,500 people are feared dead, while many thousands more may be buried beneath collapsed buildings or injured, state media have reported.
The 7.8 magnitude earthquake on Monday afternoon was felt across a huge swathe of Asia, causing buildings to sway as far away as Beijing and Bangkok.
Those closest to its epicentre, 92km (57 miles) north-west of the provincial capital Chengdu, have told of their shock and described the immediate aftermath.
Casper Oppenhuisdejong, who works for a Dutch company in the city of 10 million, told the BBC there were initially a series of minor tremors.
"All of a sudden I felt minor shocks and within seconds everybody was up. It was getting more and more intense, everybody ran out," he said.
The road started swaying as I was driving. Rocks fell from the mountains, with dust darkening the sky over the valley
Employee, Sichuan Province Seismological Bureau
"We were in quite a narrow street where everything just started shaking. All the alarms of the cars around went off, all the windows you heard smashing into each other," he added.
"Entire buildings were being evacuated, people were panicking, especially since the phones didn't work. It was mayhem. Traffic got jammed, it was very surreal."
An employee of Sichuan's seismological bureau told China's state-run Xinhua news agency that he had been driving near the epicentre when the earthquake struck.
"The road started swaying as I was driving. Rocks fell from the mountains, with dust darkening the sky over the valley," he said.
Gilles Barbier, who was staying in Chengdu at the time, told the BBC there was no major damage to buildings, but that aftershocks were causing concern.
Gilles Barbier: 'It was very scary'
"In the past two hours, I think every 20 minutes, 30 minutes, we can feel the ground shaking."
Ronen Medzini, an Israeli student, told the Associated Press by text message that power and water supplies and communications had been severely disrupted.
"Traffic jams, no running water, power outs, everyone sitting in the streets, patients evacuated from hospitals sitting outside and waiting," he said.
In the nearby city of Dujiangyan, which was closer to the epicentre, desperate efforts are under way to find survivors underneath the rubble of a three-storey school building which collapsed, burying an estimated 900 students.
It was around 2:30 pm, and the building suddenly began to rock back and forth
Reporters from Xinhua said local residents and rescue workers were pulling people out of the rubble of Juyuan Middle School as anxious parents looked on.
"Some buried teenagers were struggling to break loose from underneath the ruins while others were crying out for help," Xinhua reported.
Gao Shangyuan, a local resident helping with the rescue effort, told Xinhua he had run out of his house when the earthquake had struck and saw some students escape before the building collapsed.
"Some had jumped out of the window and a few others ran down the stairs that did not collapse," he said.
Two girls said they managed to escape because they had "run faster than the others", Xinhua added.
"It was around 2:30 pm, and the building suddenly began to rock back and forth," one of them said.
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