BEIJING—Another blast struck a residential area in a southern Chinese city Thursday, a day after more than a dozen parcel-bomb attacks hit the area, as authorities stepped up local security measures.

It was unclear whether there were any casualties from Thursday’s explosion, which damaged a six-story building in Liucheng, according to government news agency Xinhua. On Wednesday, a series of 17 blasts hit scattered locations, including a shopping mall and the dorm of a local animal husbandry bureau, killing at least seven and...