Three people are confirmed to have died and another three are seriously injured following the attack on Saturday at around 7pm.
A 25-year-old man, from Reading, was arrested at the scene on suspicion of murder and is currently in custody.
Thames Valley Police said they have launched a murder investigation and are keeping an open mind as to the motive, and although they are not currently treating it as a terrorist-related incident they are being supported by colleagues from Counter-Terrorism Command.
Graphic video has appeared on social media of at least two bloodied people being given CPR. Authorities have urged people not to share such content.
Detective Chief Superintendent Ian Hunter, of Thames Valley Police, said: "We have made one arrest and at this stage we are not looking for any other people in connection with this incident.
"There is no intelligence to suggest that there is any further danger to the public, however we urge people to remain vigilant and report anything suspicious by calling police.
"This is not currently being treated as a terrorism incident, however officers are keeping an open mind as to the motivation for the incident and are being supported by colleagues from Counter Terrorism Policing South East."
Images have emerged of police carrying out an armed operation at a block of flats in Reading where the suspect was apparently held.
Sky News' home affairs correspondent Mark White said: "A block of flats, about two miles from the park where the stabbings took place, was raided by counter-terrorism specialist firearm officers.
"There was the sound of an explosion inside the building after all residents were taken to safety.
"The building is believed to be the home address of the 25-year-old man, understood to be a LYBIAN national resident in the UK, who was arrested and is now in custody."
In response to the attack, Prime Minister Boris Johnson tweeted: "My thoughts are with all of those affected by the appalling incident in Reading and my thanks to the emergency services on the scene."
Counter-terrorism specialist firearm officers at a block of flats off Basingstoke Rd in Reading after an incident at Forbury Gardens
