A group of children and teenagers aged between 11 and 15 have admitted to torturing, killing, and burying a 6-year-old boy in Mexico, in what they considered to be a game, according to the authorities.

An 11-year-old boy, two girls aged 13, and two 15-year-old boys kidnapped Christopher Raymundo Martinez on Thursday, the Chihuahua state prosecutor’s office said in a statement.

The children had allegedly invited Christopher to play with them and collect firewood at a waste ground near his home in the northern Mexican city, but later told him they planned on pretending to kidnap him, the Daily Mail reported.

The gang then tied up the young child and almost strangled him with a bar, before they stoned him and stabbed him in the back.

The 6-year-old’s body was found face down in a shallow grave in Chihuahua two days after he died, where the children had allegedly attempted to cover him with weeds and a dead animal, the authorities said according to the Daily Mail.

Officials made the discovery after the mother of one of the 15-year-olds phoned the police to alert them that her son had taken part in the killing, the Mirror reported.

Prosecutors working on the case have expressed their concern that the brutal killing shows “social decomposition” and an “absence of values” among the group.

State prosecutor Serge Almaraz said the group had admitted to killing Christopher during a “game of kidnap” on Thursday.

“While they were playing, one of the 15-year-olds suggested to the others that they should kill Christopher. It wasn't planned. It was a condition of the game they played,” he told El Diario de Chihuahua, according to a translation by New York Daily News.

The two 15-year-old are facing criminal charges, while the young children were handed over the juvenile authorities as they are too young to be tried under local laws.