Four boys and a girl have been arrested on suspicion of conspiracy to commit murder, after a 13-year-old boy was stabbed to death in Reading.
Officers were called just before 16:00 GMT on Sunday following reports of an attack in Bugs Bottom fields, Emmer Green.
The boy was pronounced dead at the scene and police are appealing for witnesses to come forward.
The five teenagers, all aged 13 or 14, remain in police custody.
Thames Valley Police said the boy’s next of kin had been informed, but no formal identification had taken place.
A “considerable police presence” will be in place for several days.
Det Supt Kevin Brown, from Thames Valley Police, said: “This is a tragic and shocking incident which has resulted in the death of a young boy.
“We have specially-trained family liaison officers supporting the boy’s family and the thoughts of all of us within the force are with them at this extremely distressing time.”
Police are appealing for anyone who was in the area between 15:00 and 16:30 GMT on Sunday who might have taken photos or camera footage to contact them if they notice anything suspicious.
Det Supt Brown said he believed there would have been witnesses to the “dreadful incident” as the area is popular with dog walkers.
A man said his wife was walking their dog through the park on Sunday afternoon when she saw a boy on the ground with several people around him trying to give him first aid.
Another dog walker said she saw a group of youths standing around the woods in Bugs Bottom Fields at about 15:30 GMT on Sunday, describing it as “slightly unusual”.
Reacting to the news, Reading East MP Matt Rodda offered his “deepest condolences” to the boy’s family.
I would like to offer my deepest condolences to the family of the boy who was killed in an incident in Emmer Green yesterday. Please contact @ThamesVP if you have any information #rdguk #Caversham #EmmerGreen
— Matt Rodda (@MattRodda) January 4, 2021