A man is in a critical condition in hospital following a daytime attack involving about 20 people in a Cardiff park.
South Wales Police have arrested two people following Monday's incident at Tremorfa park at about 13:45 GMT.
A 26-year-old man from Tremorfa and a 17-year-old boy from Cathays are being held while others are being sought.
The victim, 19, from the Trowbridge area, was taken to the University Hospital of Wales, Cardiff.
Det Insp Tracey Rankine said: "This was a very serious incident which involved around 20 people. While two have already been arrested, further people are being sought."