At least 8,700 people are dead and thousands more injured after a massive earthquake rocked southwest China on Monday afternoon. The quake, measuring 7.8 on the Richter scale, was the worst to strike China since the Tangshan earthquake in 1976, which claimed 242,000 lives. The violent quake jolted Wenchuan County, 159 kilometers northwest of the provincial capital Chengdu, at 2:28 p.m. Monday. A spokesman with China Seismological Bureau (CSB) said the intense quake was felt in at least 16 provinces, municipalities and autonomous regions, including Beijing, Shanghai and Tibet. The shocks, which were even felt in the Thai capital of Bangkok, 1,800 kilometers from the epicenter, leveled buildings, cut transport and electricity supplies, and caused flights to and from the affected areas to be canceled or postponed. Chinese Premier Wen Jiabao, who arrived near the quake center Monday afternoon by plane, said the quake was a "major disaster" and called for calm and courage. Officials in Sichuan said at least 8,533 people were dead in the province as of 10 p.m. Monday. In Beichuan, another county hard hit by the quake, the number of people dead is estimated at 5,000, and up to 10,000 people are injured.  The quake also forced several major highways and expressways in southwestern Sichuan and northwestern Shaanxi provinces to close, according to the Ministry of Transport.  Dozens of flights at Chengdu Shuangliu International Airport and trains departing from Chengdu were suspended. Communication between the quake-hit area and outside was seriously disrupted. Telecommunications networks in the cities of Chengdu, Leshan, Mianyang and Deyang in Sichuan were paralyzed. President Hu Jintao called on government departments involved in disaster relief work to organize immediate first aid for the people and to ensure public safety. Premier Wen Jiabao arrived in Chengdu late Monday and was in Dujiangyan to direct rescue work. "My fellow Chinese, facing such a severe disaster, we need calm, confidence, courage and efficient organization," he said. "I believe we can certainly overcome the disaster with the public and the military working together under the leadership of the Central Committee of the Communist Party of China and the government." Immediately after the quake, China's earthquake administration launched a "top-level emergency contingency plan" and organized a team of 180 people to be sent to Wenchuan for disaster relief.