Officers were called at 2.56pm on Tuesday after reports of a group of people fighting in Dormington Road, Paulsgrove.
Three people were taken to hospital for injuries believed not to be life threatening, including a 17-year-old boy suffering from a stab wound to his ankle and an 18-year-old with stab wounds to his back and side.
Police have arrested a 19-year-old man and a 17-year-old boy from Portsmouth on suspicion of causing grievous bodily harm. They are in custody.
A 17-year-old boy from Fareham has also been arrested on suspicion of causing grievous bodily harm with intent, and he also remains in police custody.
A spokeswoman from Hampshire Constabulary said: ‘Officers will remain in the area today conducting enquiries and anyone with concerns, questions or information is asked to approach them.
‘We would like to reassure the local community that we believe this to be an isolated incident at this time, with no wider risk to the public.’
‘If anyone has any information or Ring Doorbell, mobile phone or Dash Cam footage of this incident, they should contact us on 101 quoting 44210480717.’
The MP for Portsmouth North, Penny Mordaunt, thanked the police for their ‘courage’ in dealing with the serious incident.
In a tweet, the MP wrote: ‘My thanks to @PompeyPolice @HantsPolice and other responders for their professionalism and courage in dealing with a serious incident in Paulsgrove today.
‘Thanks too for the reassurance to the community.’