Chinese state media say a man stabbed 22 children and an adult at an elementary school in central China on Friday.

The official Xinhua news agency says the knife-wielding man attacked the children outside a school in Chenpeng village in Henan province. It said the children, whose ages are not known, suffered non-life-threatening injuries.

Police say the attacker was later detained, but gave no motive for the stabbings.

Schools in China have increased security following a series of deadly attacks on students in recent years, mostly involving mentally unstable men.

The most recent was in August, when a man broke into a middle school in the southern city of Nanchang and stabbed two students.

In March 2010, a man described as an unemployed middle-aged doctor killed eight children with a knife at a school in the southern city of Nanping.

Some observers say the attacks have highlighted a weakness in the Chinese medical system's ability to diagnose and treat psychiatric illnesses, which have been on the rise as many are unable to cope with the rapid pace of social change.