China's investigative authorities say a knife-wielding man went on a rampage in a school in the city of Wuxi in Jiangsu Province on Saturday, killing eight people and injuring 17 others.

Police arrested a 21-year-old man on the spot and have been questioning him. The suspect graduated from the school earlier this year.

Based on their initial probe, police say the man had been frustrated that he could not receive a graduation certificate because of poor exam results.

The incident occurred just days after a hit-and-run incident in the city of Zhuhai. Thirty-five people were killed and 43 others injured at a sports facility.