KUNMING, CHINA -- Four days after a pair of bus bombs killed two people in this city of three million in southwestern China, buses are running again, though with fewer passengers and with Public Security Bureau officers firmly on board. But with the Olympics just two weeks away, the bus blasts--7/21, as the Chinese press has dubbed them--show the complexity of the security challenge facing Beijing.

Over the past few months, as the Chinese government has preoccupied itself with quashing dissent in Tibet and Xinjiang, Kunming--sedate, but equally far from Beijing, and home to its own share of ethnic minorities--seems to have slipped under the radar. When it became clear that the blasts were manmade, some Western news organizations pointed to disgruntled rubber farmers from a rural area of Yunnan inhabited by the Dai minority. One could be forgiven for asking: the who? Turns out they clashed with police officers in a deadly riot last week. But so did peasants in Guangdong province. Then there was that incident in Guizhou, just east of Yunnan, last month: over 10,000 rioters in all.

To add to Beijing's load, locals are spreading September 11-style conspiracy theories. The Kunming Daily published a report stating that the night before the bombings a text message circulated urging recipients to stay away from certain bus lines. The message was signed "the mobilizer of nobodies." The government responded by singling out nobodies, requiring all residents of migrant neighborhoods to register with the police. This is, we can only guess, not the best way to regain local support.

Back in Beijing, the government is taking other precautionary measures. There's been a clamp-down on visa issuances in an effort to keep out protestors, along with the thousands of Christian missionaries who had planned to descend on Beijing for a "spiritual harvest." If suspicious foreigners still manage to sneak in, however, police are equipped with the English phrases necessary to interrogate them. Meanwhile, in Shenyang, site of some soccer events, cab drivers are doubling as spies.

But 7/21 shows that with the opening ceremony just two weeks away, the government has much more than outsiders to fear. On one Chinese message board, a commentator observed, "America's terrorists are foreign. China's terrorists are Chinese ... tragic."

--Mara Hvistendahl