Beijing, May 12 (Xinhua) China has dispatched troops to Wenchuan County in China's southwestern Sichuan Province to help in the disaster relief work after a massive earthquake measuring 7.8 on the Richter scale jolted the region Monday.

Officials in the Chongqing Municipality said as per initial report four people were killed in the quake. All the victims were primary school students. Around 100 students were reportedly injured when their school collapsed in the outer Liangping County of Chongqing, a local government official said.

Tian Yixiang, an officer with the People's Liberation Army (PLA), said the troops will assist the local government in the Wenchuan County and will monitor the situation to carry forward the disaster relief work.

According to the State Seismological Bureau, an earthquake measuring 7.8 on the Richter scale jolted the Wenchuan County at 2.28 p.m. Monday. Its epicentre was located 31.0 degrees north latitude and 103.4 degrees east longitude, the bureau said.

Meanwhile, Chinese President Hu Jintao has ordered all-out efforts to rescue the quake-hit victims. Premier Wen Jiabao is one his way to the Wenchuan County.

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

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

Another earthquake measuring 3.9 on the Richter scale jolted Tongzhou District in east Beijing at 2.35 p.m. Monday. The quake's epicentre was located 39.8 north latitude and 116.8 east longitude, according to the State Seismological Bureau.

Tremors were also reported from many other parts of China. Reporters in Chengdu said residential buildings in downtown areas were damaged.

The telecom networks in Chengdu and Chongqing cities snapped after the quake. People complained they were unable to make telephone calls on the fixed line or in the mobile.

The quake was also felt in Zhengzhou, capital of central Henan Province, where people rushed out of homes and offices and took to the streets.

Many said they felt dizzy and saw the pendant lamps on their ceilings swinging back and forth.

In Lanzhou, capital of the northwest China's Gansu Province, the quake sent many parked cars by the roadside buzzing.

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

A retiree in Leshan City of Sichuan Province said over the telephone that a wall in her garden collapsed, while a repairman in Chongqing saw the ceiling of his factory collapsed. In Shanghai, people were evacuated from office buildings in Hongqiao and Nanjing Road.