Two teenagers have been stabbed in a lakeside fight involving at least 10 people.
Police were called to Furzton Lake in Milton Keynes at about 19:30 BST on Tuesday.
Thames Valley Police said the men, aged 18 and 19, had non-life threatening knife injuries and were taken to hospital for treatment.
It said two boys, aged 17 and 15, and an 18-year-old man, were arrested on suspicion of assault.
In response to the incident, a 24-hour Section 60 order has been put in place for the whole borough of Milton Keynes, the force said.
It said the order came into effect at 10:47 BST on Wednesday and it means officers have the power to stop and search people, regardless of whether they have reasonable grounds to or not.
Police said the confrontation happened on a Redway foot and cycle path and it was believed the victims and the offenders were known to each other.
Insp Nick Herceg said: "This incident happened early in the evening and involved a number of young people with weapons.
"Two teenagers have suffered injuries, but thankfully these are not life-threatening, although clearly this is a very serious incident."
Police appealed for witnesses.