An explosion at the gates of a Chinese kindergarten that killed eight people was caused by a 22-year-old man who died in the blast, police say.

Bomb-making materials were found in the flat where the man, named as Xu, lived, and the words “die” and “death” had been scrawled on the walls.

The blast happened just as parents in Fengxian in the eastern province of Jiangsu were picking up their children at the end of the day.

It is being treated as a criminal act.

Xu had suffered from health problems and had dropped out of school but was employed, police said. More than 60 people were injured in the explosion, including eight who are in a serious condition, the authorities say.

A survivor told Chinese state TV that the kindergarten gate had just opened for children to leave but none had come out when the blast happened.

Fengxian officials said none of the children or teachers at the kindergarten were among the casualties.