CHENGDU, China - A powerful earthquake toppled buildings, schools and chemical plants Monday in central China, killing about 10,000 people and trapping untold numbers in mounds of concrete, steel and earth in the country's worst quake in three decades.

The 7.8-magnitude quake devastated a region of small cities and towns set amid steep hills north of Sichuan's provincial capital of Chengdu. Striking in midafternoon, it emptied office buildings across the country in Beijing and could be felt as far away as Vietnam.

As Tuesday dawned, rescuers were frantically searching for more survivors, but rain was compounding the difficulty. Premier Wen Jiabao, who flew to the region, said rain was forecast for the next several days.

The government was pouring in troops to aid in the disaster recovery. Xinhua said 16,000 were in the area and 34,000 more were en route.

The earthquake also rattled buildings in Beijing, 930 miles to the north, causing evacuations of office towers. People ran screaming into the streets in other cities, where many residents said they had never felt an earthquake.

In Beijing, where hundreds of thousands of foreign visitors are expected for the Olympics, stadiums, arenas and other venues for the games were undamaged.

"The Olympic venues were not affected by the earthquake," said Sun Weide, a spokesman for the Beijing organizing committee. "We considered earthquakes when building those venues."