The blasts struck at 7:05 and 8:10 a.m., state media reported. Public security officials in Kunming, the capital of Yunnan Province in southwestern China, provided no information about whether the explosions were coordinated, nor did the authorities say whether they were the work of terrorist groups or disgruntled individuals.
By Monday afternoon, the police were still searching for suspects. Checkpoints were set up on highways, while the police were tightening security at Kunming’s airport and train terminal, according to the Web site of the provincial public security bureau. A photograph of one bus posted online showed shards from a shattered window spread across a street but also suggested that the blast had not been powerful enough to inflict catastrophic damage.
China has experienced a spate of riots and public protests as the country prepares for the Aug. 8 opening ceremonies of the Beijing Olympics.
In recent years, public protests have become common in China, especially in rural areas where farmers have demonstrated against illegal land seizures and official corruption. But the authorities are trying to tamp down embarrassing outbursts ahead of the Olympics and have ordered local authorities to address local grievances and block petitioners from coming to Beijing.
As many as 30,000 people rioted in Weng’an County, in Guizhou Province, in late June, in response to allegations that the local police had mishandled the investigation of the death of a teenage girl. Last week, a mob of 100 angry protesters attacked a village police station in Guangdong Province in an uprising over allegations of police malfeasance.
Last weekend, the police in a rural region of Yunnan Province killed two people after a violent clash with 500 rubber farmers. The farmers, armed with knives, injured 41 police officers and damaged several police cars in a confrontation rooted in a long-running dispute between farmers and a local rubber company, state media reported. Provincial officials are investigating the attack.
Beyond the escalating internal disturbances, the authorities are warning that foreign terrorist groups may be plotting to disrupt the Olympics. Chinese officials have singled out the Eastern Turkistan Islamic Movement and say they destroyed 41 training bases and arrested 82 people.
“Intelligence reports show the group has been planning to carry out terrorist attacks during the Games,” Ma Zhenchuan, director of Olympic security, told China Central Television.
Some human rights advocates say China is exaggerating the threat posed by the group to justify a broad security crackdown in Xinjiang, the restive western region that is home to the country’s Muslim Uighur population.
In Kunming, the first bus blast killed Wang Dezhi, a 30-year-old woman, while injuring 10 other people, according to the provincial public security Web site. The second explosion was 65 minutes later on a bus following the same route. In this blast, a 26-year-old man, Chen Shifei, died and four people were injured.
Witnesses on one bus told Chinese newspapers that a short man in a black shirt and gray pants boarded the bus before the explosion and sat behind the driver. After the bus stopped and then prepared to get going again, the man jumped up and yelled for the driver to let him off, the witnesses said.
Witnesses told a joint reporting team from the Yunnan Information Daily and the Southern Newspaper Group that the man had left a black leather bag on the bus. About 30 seconds later, the bus exploded. Witnesses on the second bus told Chinese journalists they had also seen a black bag.
Ms. Wang was returning with her husband to celebrate the birthday of their 5-year-old daughter. Her husband suffered minor injuries in the explosion.
With more than three million residents, Kunming is a temperate city that serves as a gateway to some of China’s most scenic areas in outlying Yunnan Province. It serves as a transportation hub to Southeast Asia and is known for its high percentage of minority communities in the province’s mountainous regions.