Two public buses exploded during the Monday morning rush hour in the city of Kunming, killing at least two people and injuring 14 others in what the authorities described as deliberate attacks as China is tightening security nationwide and warning of possible terrorist threats in advance of next month's Olympic Games.
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 provincial public security bureau.
China has experienced a spate of riots and public protests as it prepares for the Aug. 8 opening ceremonies of the Beijing Olympics.
The authorities warn 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.
In Kunming, the first bus blast killed Wang Dezhi, a 30-year-old woman, while injuring 10 others, according to the provincial public security agency.
The second explosion followed 65 minutes later on a bus following the same route. In this blast, a 26-year-old man, Chen Shifei, died and four 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 reporters 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.
With more than 3 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.