Police in an east China city are looking into allegations that a couple have severely abused their adopted child.

Police in Nanjing City, Jiangsu Province, said in a statement on Saturday that the couple in Nanjing were suspected of severely beating up the child, surnamed Shi.

The statement said that the boy's teacher alerted police on Thursday when the nine-year-old showed up in school with severe bruises on his body.

Pictures circulated on the internet show bruises in the child's back, legs, arms, belly and feet.

An investigation is under way, said the Nanjing police.

Last month, a six-year-old girl in Yiwu City, east China's Zhejiang Province, was allegedly beaten to death by her mother during a "family dispute", triggering calls for better protective measures for minors.

Of the 697 child abuse cases exposed by the media from 2008 to 2013, 74.75 percent were committed by parents, the Beijing Youth Legal Assistance Research Center revealed.