Six people are in custody after being arrested in connection with the death of teenager Amar Aslam in the walled garden of a park.
The battered body of 17-year-old Amar was discovered by two passers-by in Crow Nest Park in Dewsbury, West Yorkshire, on Sunday evening.
Officers arrested two boys aged 12 and 13, two boys aged 15 and a 20-year-old in connection with the death, West Yorkshire Police said.
They later confirmed another 15-year-old boy had been arrested in connection with the murder.
A post-mortem examination revealed that Amar died of head injuries after a "sustained and brutal" attack, police said.
It is feared Amar may have been the victim of violence between warring gangs of youths in the park.
Detectives are investigating whether there is a link between the boy's death and the fighting.
Dewsbury MP Shahid Malik called for "a change in society" following the murder, which happened very close to his home.
He said the problem facing society was that many young people were part of a culture where violence was seen as an acceptable way of life.
Police on Monday closed the whole of Crow Nest Park as forensics experts examined the scene in the walled garden.
