In Shifang, where two chemical plants collapsed, releasing a huge toxic cloud, about 600 people were reported dead and up to 2,300 still buried.
Sichuan Vice-Governor Li Chengyun said the death toll included: 7,395 in Mianyang, 2,648 in Deyang City, 959 in the provincial capital Chengdu, 700 in Guangyuan City, and 161 in the Aba Tibetan and Qiang Autonomous Prefecture.
Later there were reports that 3,000 were dead in Mianzhu.
Prime Minister Wen Jiabao promised no effort would be spared to rescue those trapped and look after the survivors.
"We will save the people," he declared through a loudhailer to people in Shifang.
But he expressed frustration that rescue efforts were being held up by testing conditions.
"The disaster situation is worse than expected, and the rescue sites are quite complex," he admitted.
The BBC's Michael Bristow, in Dujiangyan, says aftershocks have struck regularly.
People are too fearful to return to their homes, he says, and are spending another night in the open, in heavy rain, with no power or water.
Children pulled from the rubble at the school in Dujiangyan
"I'm cold. I don't dare to sleep, and I'm worried a building is going to fall down on me," 20-year-old waitress Tang Ling told the Associated Press (AP).
"What's happened is so cruel. In one minute to have so many people die is too tragic."
People have set up tents or makeshift shelters on almost any piece of open land, even in the middle of road junctions.
Some 10,000 refugees were packed into Mianyang's Jiuzhou Gymnasium, where empty water bottles, boxes of instant noodles and cigarette cartons littered the ground, AP reported.
The health ministry has made an urgent appeal for people to give blood to help the injured.
RECENT CHINA QUAKES
March, 2008: 7.2 quake in Xinjiang - damage limited
February 2003: 6.8 quake in Xinjiang - at least 94 dead, 200 hurt
January 1998: 6.2 quake in rural Hebei - at least 47 dead, 2,000 hurt
The 7.9-magnitude quake struck on Monday at 1428 local time (0628 GMT) and was felt as far away as Beijing and the Thai capital, Bangkok.
It was the worst to strike China in three decades - since more than 240,000 people were killed in Tangshan in 1976.
The worst affected area has been south-western Sichuan province, but more than 300 deaths have also been reported in the neighbouring provinces of Gansu and Shaanxi, and in Chongqing municipality.
China's Olympic Games organisers say they will scale down the route of the torch through the country and there will be a minute's silence when the next leg starts in the south-eastern city of Ruijin on Wednesday.
US President George W Bush expressed condolences to victims' families, while the US, UK, the European Union, Japan, South Korea and Taiwan reportedly offered aid.
China said it would gratefully accept international help to cope with the quake.
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