BEIJING — A series of explosions targeting public buildings in a small city in southern China killed at least six people and injured dozens on Wednesday, officials and state media said. The official Xinhua News Agency said there were 15 blasts in Liucheng county in the southern region of Guangxi and that six people were killed. The city government of Liuzhou, which oversees Liucheng, said the explosions also injured 13 people, although later reports by state media said dozens were injured. Authorities said they did not know who was responsible for the explosions, but were investigating them as a criminal case. “There were so many of them, and they were so loud, everyone in the county could hear them,” said a hotel employee who gave only his family name, Li. The hotel is near a township office building that was hit by one of the explosions. “They sounded like someone was blasting rocks in the mountains,” Li said. The explosions, which occurred between 3:15 p.m. and 5 p.m., hit a hospital, local markets, a shopping mall, a bus station and several government buildings, including a jail and dormitories for government workers, according to a police statement posted by the local newspaper Nanguo Zaobao. Liuzhou's police chief, Zhou Changqing, said the blasts were triggered by explosive devices delivered in several mail packages, state broadcaster CCTV reported. Zhou said the case was under investigation. He did not name any suspects or offer any motive for the explosions. A supermarket employee said the store was evacuated immediately when an adjacent supermarket was hit by the explosives. “All of us heard the blast. It was very loud,” he said. Photos posted online showed streets filled with smoke, strewn debris, dust clouds in the sky and the rubble from a five-story building that partially collapsed. Xinhua said at least one more explosion hit downtown Liuzhou, away from Liucheng county, but did not say whether there were any casualties. — AP