At least seven people were killed and 31 injured after three separate bomb blasts rocked China over the weekend, including one at a Carrefour shopping center in central Wuhan city, state press reported Monday. Four people were killed and 23 injured in central China's Hubei province when an explosion occurred as firemen and medical workers were trying to fight a blaze at a government institute early Sunday morning, the China Daily said on its website. The blast occurred in the middle of the night in the city of Yichang, close to the massive Three Gorges Dam on the Yangtze River. Emergency rescue workers had been called to fight the blaze at a two-storey dormitory building of a company belonging to the Hubei geological survey team, the report said. While firefighters fought the blaze and medical workers began treating residents in the dormitory, a sudden explosion sent firemen and rescue personnel sprawling to the ground. "Suddenly an unidentified person threw some kind of explosive into the scene," the report, citing eyewitnesses, said. Not long after the explosion, a man committed suicide by self-immolation in a warehouse in the compound, it said. Officials and police, when contacted Monday, refused comment on the incident, saying an investigation was under way. A 12-year old child was among the dead, the China Daily said. In a separate blast Sunday evening in the Hubei provincial capital of Wuhan, three people were slightly injured when a bomb went off in a Carrefour shopping center in the Hanyang district, the Wuhan Evening News said. The bomb went off in a hallway between a Kentucky Fried Chicken restaurant located within the Carrefour complex and the actual shopping center, it said. Residents reported hearing two explosions at the time. French retailer Carrefour was the target of a string of bombings that occurred in three cities in late 2001, while the US-owned Kentucky Fried Chicken was earlier this year targeted in a series of bombings at Western fast food restaurants in Xian city, northern China's Shaanxi province. Meanwhile, three people were killed and five injured when a bomb went off in Baoji city, Shaanxi province late Sunday, the Chinese Business View reported. Witnesses said the bomb was concealed in a metal box and was dropped off by a vehicle in a residential district. A woman who went to pick up the box was killed instantly after it exploded, while the driver of the vehicle was slightly injured, it said. The incident is under investigation. **PHOTO CAPTION*** French supermarket chain Carrefour, which has been targeted in other bombs attacks in China, has again been hit by apparent bombers. (AFP/File /Goh Chai-hin)