100,000 security forces on alert for Olympics

Ten thousand athletes have gathered in China for the Olympics, along with hundreds of thousands of fans and 30,000 journalists. All are being watched over by 100,000 security forces.

In Beijing, heavily armed police roam the airport. Subway passengers must submit to bag checks and go through X-ray machines. The National Stadium is protected by anti-aircraft guns.

"The Chinese are clearly hyper-focused and hyper-worried about security, and this is something they've been working on for at least three or four years by now," said David Finklestein, an expert on China who serves as the director of the China Studies Center.

Officials stepped up security measures after an attack Monday in the city of Kashgar killed 16 police officers and wounded 16 others. Kashgar is 2,500 miles from Beijing in northwestern China. - cnn