Police arrested three boys and took them into custody after they allegedly bullied and killed the junior high school student in the small city of Handan on March 10, and then buried him in a shallow pit, state media reported. So far, no charges have been made.

Local police are investigating the case as a homicide and have set up a team of more than 60 people to probe the case, state media broadcaster CCTV News reported. Police in Handan's Feixiang District declined to comment, and district propaganda officials referred Reuters to CCTV reports on the case.

State media said the victim and the three boys in custody were children of rural migrant workers who spend most of the year working in large cities, leaving childcare duties to grandparents and other relatives.

There are nearly 67 million of such so-called "left behind" children, 2020 census data shows, and academic studies show that these children are at higher risk of mental health issues, becoming victims of bullying and criminal behaviour.

The case has gripped the nation, with many Chinese taking to social media to express their outrage.

"Public Trial! National live broadcast," wrote a user on Chinese social media platform Weibo. Other users called for the perpetrators to be punished, while some said that bullies across the country were watching the outcome.

In 2021, China lowered the age of criminal responsibility from 14 to 12 for certain crimes. The Global Times, citing experts, said the case could be the first that goes to court under the new legislation.

Beijing-based defence lawyer David Zhang told Reuters the crimes the law covered include intentional homicide, intentional injury causing death and injuring someone by cruel means resulting in disability.

"Although China has a strict censorship system... a considerable number of teenagers have precocious ideological maturity and social cognitive abilities far exceeding their peers," he added.

(Reporting by Bernard Orr and Laurie Chen; Editing by Miral Fahmy)

By Bernard Orr and Laurie Chen