More than 700 people were confirmed dead and thousands more were feared dead after an earthquake measuring 7.8 on the Richter scale caused widespread damage to parts of south-western China on Monday, reported dpa.
At least 592 people died in Sichuan province and a total of 134 people died in the neighbouring regions of Shaanxi, Gansu, Chongqing and Yunnan, the semi-official China News Service and other state media said.
The death toll was expected to climb significantly, the reports said.
Beichuan county in Sichuan province reported that between 3,000 and 5,000 people were feared dead after the earthquake caused 80 per cent of buildings to collapse, the official Xinhua news agency said.
The agency said officials also estimated that about 10,000 people were injured in Beichuan, which is about 100 kilometres from the epicentre of the earthquake.
By late Monday evening there were still no reports from Wenchuan county, the nearest town to the epicentre, which which has a population of 112,000.
The earthquake struck at 2:28 pm (0628 GMT) in Wenchuan county, and could be felt in cities hundreds of kilometres away, including Beijing, Shanghai, Hong Kong and Bangkok.
At least four teenagers were confirmed dead after the earthquake caused school buildings to collapse and bury nearly 900 students at the Juyuan Middle School in Sichuan's Dujiangyan city, about 100 kilometres from the epicentre, reports said.
One Dujiangyan resident told Deutsche Presse-Agentur dpa by telephone that her five-storey apartment block and many other buildings in the city were seriously damaged by the earthquake.
The woman said she and her family were staying outdoors on a playgroud but had no umbrellas or waterproof jackets to protect them from rain falling on the city.
A spokesman for the Sichuan provincial seismological bureau told Xinhua that "whole rows of houses" had collapsed in Dujiangyan.
Several hundred workers were buried after two chemical plants collapsed onto them in Sichuan's Shifang city.
Some 80 tons of ammonia leaked from the plants, forcing the evacuation of 6,000 residents in Shifang.
The earthquake also affected Sichuan's capital, Chengdu, and nearby Chongqing.
At least 45 people died in Chengdu, where officials suspended rail and air services, the provincial government said.
More reports of casualties came from Chongqing's Liangping county, where four children died and more than 100 were injured at two primary schools which collapsed during the earthquake.
The local government of Aba prefecture, which administers Wenzhou, said all traffic was cut to Wenchuan and the nearby Lixian and Maoxian, with landslides and extensive damage to roads and buildings also reported in other areas of Aba.
Initial reports put the magnitude at 7.6 but the State Seismological Bureau later upgraded it to 7.8, while an official at the Beijing Seismological Bureau said it was measured at 8.0.
The government declared a "level II" emergency, the second-most serious category, to respond to the earthquake damage.
Premier Wen Jiabao arrived in Chengdu and was travelling to Wenchuan to supervise rescue work, urging officials and members of the ruling Communist Party to "work on the front line" to lead relief efforts.
President Hu Jintao also issued a statement urging "all-out efforts to help those affected" by the quake, which was followed by at least six aftershocks measuring 5.0 or higher on the Richter scale.
The People's Liberation Army dispatched 5,000 troops from Chengdu to help in rescue work and damage assessment in Wenchuan.
The central government also organized two military transport planes to carry 184 disaster relief, medical and seismological experts from Beijing to Sichuan.
In Brussels, meanwhile, the European Commission said it was ready to offer China aid following the earthquake.
A tremor measuring 3.9 on the Richter scale was recorded in Beijing's eastern suburb of Tongzhou at 2:35 pm, while workers were evacuated from some major office towers in Shanghai.
State television ran a statement from the Beijing seismological bureau to deny rumours that it had forecast a strong earthquake for the city in the next few days.
In Hong Kong, people rang emergency services in panic when the earthquake made the ground shake and buildings sway.
Lee Chia-yen, a spokesman for Taiwan's Travel Agent Association, said it was trying to locate 2,360 Taiwanese tourists from nine tour groups travelling in Sichuan.