Two people have been killed in explosions on two public buses in the Chinese city of Kunming this morning.
Police said the blasts were deliberately set off in an incident likely to heighten Olympic security concerns.
The blasts occurred about an hour apart during morning rush hour traffic in downtown Kunming, the capital of southwest China's Yunnan province.
'According to preliminary investigations, the explosions were cases of man-made, deliberate sabotage,' a spokesman with the Yunnan Public Security Bureau told wire services, without giving further details.
The incidents add to tensions ahead of next month's Beijing Olympics, stoked by repeated warnings from the Chinese government about a terrorism threat facing the games.
The government also has expressed deep concern about social unrest marring its efforts to portray the country as 'harmonious and stable' ahead of the Olympics, amid recent violent protests in Yunnan and elsewhere.
The first blast occurred at about 7am local time (midnight Irish time), killing one woman and injuring 10 other people.
The second blast came about an hour later on the same road and killed one man, injuring four others.
Following the blasts, police cordoned off some streets in the area and carried out identity checks in a search for any 'suspicious' persons.
Kunming has a population of just over 6m people and is about 2,100km southwest of Beijing.
It is the second time an explosion on a bus has been reported in China in recent months.
In May, three people died when a public bus in Shanghai burst into flames. Police blamed the incident on flammable liquids being brought on board the vehicle but have provided no other explanation.
China has dramatically tightened security in Beijing and throughout the country ahead of the Olympics, which begin on 8 August, amid concerns over terrorism and social unrest.
It says the main terrorism threats are posed by militants in China's restive northwestern Xinjiang region.
Officials also have hinted at possible attacks by Tibetan independence supporters following an outburst of violent unrest in March that was firmly put down by China.
However there are also tens of thousands of protests each year across the country from a vast array of marginalised people who take to the streets to protest official corruption and other injustices.
In the latest incident of social unrest in Yunnan, more than 1,000 rubber plantation growers clashed with police on Saturday in a village about 400km from Kunming near the border with Myanmar.
Police killed two people in the clash, which was triggered over a dispute about the sale of the crops, according to accounts by the police and a Hong Kong rights group.
