BEIJING — A powerful earthquake hit central China yesterday, killing nearly 10,000 people, as schools and other buildings collapsed across four provinces and tremors shook buildings as far away as Bangkok.

State press outlets reported widespread damage, and officials feared that the death toll could rise sharply as rescue teams reached areas affected by the massive quake, the worst to strike the country in three decades.

Most of the damage appeared to be in Sichuan province, where as many as 5,000 people died and 10,000 were injured in one county alone, state press outlets reported. In another town, 900 students were trapped beneath the rubble of a high school destroyed by the quake.

“People were terrified,” a witness, Huang Shi Hua, said after watching rescuers loading victims into ambulances near the city of Chongqing, where a primary school had collapsed, killing four children.

The 7.9-magnitude earthquake struck at 2:28 p.m. and was centered 55 miles northwest of Chengdu, the capital of Sichuan province, according to China’s State Seismological Bureau. More than 1,000 aftershocks jolted the region, state press outlets reported, and the quake was felt nearly 1,000 miles away in Beijing, where workers poured into the streets as office towers swayed.

Premier Wen of China arrived in Chengdu just a few hours after the quake hit to oversee rescue efforts and establish a temporary headquarters for disaster relief. An estimated 50,000 soldiers, police and reservists were dispatched to the area to provide aid as President Hu called for “all-out” efforts to rescue quake victims. The deployment of the military, in particular, sent a signal of urgency in a country that carefully calibrates the use of its armed forces.

Rescuers, meanwhile, worked through the night to locate victims and provide medical care. By 11 p.m., more than 50 bodies had been recovered from the debris of the collapsed high school in Dujiangyan city, west of the quake’s center, state press outlets reported. It did not say how many had survived. A hospital in the city also collapsed, the New China News Agency reported.

The general engineer of China’s National Disaster Reduction Center, Li Jing, said the full scale of the devastation is unclear because communication and transportation links to mountainous Sichuan province were badly damaged. He said rescuers will place a priority on getting water and medicine to the affected regions as quickly as possible to minimize the loss of life.

Cellphone communication in the area failed after 2,300 base stations and five power plants shut down, officials said. Chengdu airport closed and flights throughout the country were disrupted.

Telephone calls could not be connected to emergency officials in Wenchuan county, the sparsely populated area at the quake’s center. Wenchuan, home to China’s leading giant panda reserve, is to the south of Beichuan county, where up to 80% of the buildings collapsed.

A rescue team set out for Wenchuan on foot at 10 p.m. yesterday, walked through the night, and had about 45 miles to go at about 6:30 a.m. today. Local officials, via satellite phone, appealed for urgent help.

A high-level communist party official in Sichuan, Li Chongxi, attempted to lead a rescue team to Wenchuan but could not get through. “We are doing everything we can, but the roads are blanketed with rocks and boulders,” he was quoted as telling the New China News Agency.

The massive Three Gorges Dam, a few hundred miles away, was not affected by the quake, state press outlets quoted an official as saying. Two chemical plants in Shifang city were reportedly flattened, burying hundreds of workers and spilling more than 80 tons of toxic liquid ammonia.

A Chengdu resident said the ground shook for several minutes and tall buildings swayed in the city of 10.7 million people. He saw one building shift position and begin leaning after the quake ended, but he said it had not fallen.

In Sichuan’s Deyang city, Chen Liangcai, said the quake felt like “sitting on a train going through a hard turn.” State press outlets reported that five schools collapsed in the city, trapping an unknown number of students. Mr. Chen said local officials advised residents not to go inside their homes to sleep, but to spend the night outside.

Experts said many of the buildings were not built to withstand the impact of such a severe earthquake. In the four hours following the main quake, many other, smaller quakes were recorded by the U.S. Geological Survey. Experts said aftershocks could be just as deadly as the main quake because they put new strains on already damaged structures.

One Deyang shopkeeper, who declined to give her name, said she was advised to stay in her shop and not return home for the night. Rattled after having watched dozens of ambulances race by all afternoon, she said she would do as she was told. But she devised her own early warning system by putting a piece of metal in a glass; if she noticed it trembling, she said, she would run from the shop.

A reporter for National Public Radio who was in Chengdu at the time of the quake reported that tens of thousands of people had rushed into the streets, fearing that buildings would collapse. Many people remained in the streets for several hours, she said; stores closed and did not reopen.