A major earthquake measuring 7.8 on the Richter scale jolted Wenchuan County in southwest China's Sichuan Province at 2:28 PM on Monday, the State Seismological Bureau (SSB) said, revising its previous figure of 7.6.

The epicenter of the quake was located 31.0 degrees north latitude and 103.4 degrees east longitude, the bureau said.

With a population of 111,800, Wenchuan lies in the southeast part of the Tibetan-Qiang Autonomous Prefecture of Aba, 146 kilometers northwest of Chengdu, the provincial capital of Sichuan.

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Wenchuan is home to the Wolong Nature Reserve, China's leading research and breeding base for endangered giant pandas.

Minutes later, at 2:35 PM, an earthquake measuring 3.9 on the Richter scale jolted Tongzhou District in east Beijing. That quake's epicenter was 39.8 north latitude and 116.8 east longitude, according to the SSB.

Xinhua reporters in many other parts of China also reported tremors. Reporters in Chengdu said they saw cracks on the walls of some residential buildings in the downtown area, but no building collapsed.

Telecom networks in the cities of Chengdu, Chongqing and Zhengzhou broke down for a while after the quake. People complained they were unable to complete calls on either fixed lines or cell phones.

In Zhengzhou, capital of central Henan Province, people rushed out of homes and offices.

Many said they felt dizzy and saw the ceiling light fixtures swinging back and forth.

In Lanzhou, capital of the northwestern Gansu Province, the quake set off alarms of many parked cars by the roadside.

Xinhua reporters in Yinchuan, capital of Ningxia Hui Autonomous Region, said they felt their office building rocking back and forth for about four minutes.

A retiree in Leshan City, Sichuan Province, said in a telephone interview that a wall in her garden had collapsed, while a repairman in Chongqing saw the ceiling of his factory crumble and raised the alarm among the staff, who quickly left the building.

In Shanghai, people were evacuated from office buildings in Hongqiao and Nanjing Road.

Maowen, a neighboring county of Wenchuan, was hit by an quake measuring 7.5 on the Richter scale in 1933, which claimed more than 9,000 lives. Songpan and Pingwu in the northwest of Sichuan Province were hit by an earthquake with a magnitude of 7.2 in 1976.