BEIJING - Chinese education experts have called for vigilance and enhanced monitoring of books sold as reading material for children, which increasingly contain violent or pornographic content.

During the long summer reading season, primary and middle school students can be easy prey to inferior children's books, a common concern of parents.

During recent field investigations, Xinhua reporters in Beijing and south China's Guangxi Zhuang autonomous region spotted a number of children's books tainted with violent or pornographic elements.

Among them, a science-themed bestseller carries graphic images pictures of brain injuries and a cover featuring a bloody brain.

"Mum killed me before I was eaten up by Dad. My siblings collected my bones from the dinner table and buried them in a cold, stone tomb," reads an adventure story for children.

More books that intended for kids were found to contain phrases such as "[She has] plump breasts and round hips, with hot figure," or "I want to have a baby with my elder brother."

Xia Xueluan, professor of sociology at Peking University, said the children's book market in China was in chaos with bad books mixed with good ones.

"A lot of children's books fail to embody healthy and upright values," he said, urging enhanced greater market supervision and stricter rating based of content.

Dr. Yang Tianbao, a scholar with Guangxi University for Nationalities in south China, said that such publications are never an insignificant matter: misleading and vulgar content can be very bad for children.