The strongest earthquake to hit China in more than three decades jolted Wenchuan county in Sichuan province at 2:28 pm yesterday, killing more than 8,500. Casualties are expected to rise fast.

The tremor measured 7.8 on the Richter scale, with the epicenter located at 31.0 degrees north latitude and 103.4 degrees east longitude, the State Seismological Bureau (SSB) said.

The quake was centered 10 km below the surface; and more than 300 aftershocks were reported.

A quake of the same magnitude hit Tangshan, Hebei, on July 28, 1976, killing more than 240,000.

Wenchuan is about 100 km northwest of Chengdu, provincial capital of Sichuan, and has a population of 111,800. It is home to the Wolong Nature Reserve, the country's leading research and breeding base for giant pandas.

Local authorities said 8,533 people were killed. The figure was released by the temporary headquarters for disaster relief headed by Premier Wen Jiabao in Sichuan.

Wen arrived in Dujiangyan last night to direct the rescue work.

Xinhua reported at least 30 people were killed in Wenchuan. However, the actual figure was hard to obtain as the county has been cut off from the outside world with telecom services down and roads blocked.

Most are feared dead in Beichuan county of Mianyang City - 160 km northeast of Chengdu - where the number of deaths is estimated at more than 3,000. More than 80 percent of the buildings there were destroyed and about 10,000 were injured.

In Shifang, hundreds of people were buried under two collapsed chemical plants. About 6,000 people were evacuated, Xinhua said, adding that more than 80 tons of liquid ammonia had leaked.

In neighboring provinces, 61 were killed in Shaanxi, 48 in Gansu, 50 in Chongqing, and one in Yunnan.

President Hu Jintao ordered all-out efforts to help those affected by the quake.

Zhang Hongwei, spokesman for the SSB, said the earthquake was felt in more than half of the country; and the tremors were felt as far away as Thailand and Vietnam.

Tremors were reported in Beijing, Shanghai, and Chongqing municipalities, Ningxia, Qinghai, Gansu, Shanxi, Shaanxi, Shandong, Yunnan, Hunan, Hubei, Guizhou, Henan and Jiangsu provinces, and the Tibet autonomous region, Zhang said.

The quake measured 3.9 in Beijing, according to the SSB.

Five power plants were knocked off the grid and six transformer substations were shut down in Sichuan province.

Three more power plants and two transformer substations were knocked out in Shaanxi province to the north of Sichuan, Xinhua said, citing State Grid Corp, a major government-owned utility.

There was no indication how large an area was without power.

State Grid Corp said aftershocks make it difficult to contact the affected areas for a detailed damage report, Xinhua said.

The quake caused multiple landslides and collapses along railway lines near Chengdu, leaving 180 trains stranded on the rails.

Thirty-one passenger and 149 cargo trains were stranded on Baoji-Chengdu line, Chengdu-Kunming line, Chengdu-Chongqing line and their branch lines linking Chengdu with the rest of the country.

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