Six men have been arrested on suspicion of murder and attempted murder after a man in his 20s was killed and another injured near some playing fields.
Police were on Wednesday night called near to the Edinburgh Playing Field in Aylesbury, Buckinghamshire, to reports of a large fight.
Two men were taken to hospital, and one of them, who police said is yet to be formally identified, died. The young man's next of kin has been informed.
Three men arrested on Wednesday night by Thames Valley police remained in police cells on Saturday.
Three more men, all from Buckinghamshire, were arrested on Saturday and questioned in custody.
A spokesman for Thames Valley Police said officers were in the very early stages of a murder investigation and few details of what happened were being released.
The spokesman said: "The arrests are in connection with an incident in Lembrook Walk, Aylesbury, Bucks., near to the Edinburgh Playing Fields, on Wednesday, when officers were called to reports of a large fight taking place.
"Two men were taken to hospital, where sadly, one died of his injuries. The other man suffered less serious injuries and has since been discharged."
A Home Office post-mortem examination was conducted on Friday, with results pending further medical opinion, the spokesman added.
Senior Investigating Officer Detective Superintendent Kevin Brown, head of Thames Valley Police's Major Crime Unit, said: "We are continuing this investigation and have made three further arrests.
"The next of kin of the man who has died continue to be supported by specially trained officers, and our thoughts remain with them at this difficult time.
"On behalf of the family, we would request that their privacy is respected while they come to terms with what has happened.
"I can reassure the local community again that we believe the victim and offenders were known to each other and there is no suggestion of any wider threat to the public.
"However, I am again appealing to anybody with any information that can help this investigation to please contact the 24-hour number 101."