Three people have died and three more have been seriously injured after stabbings in a park in Reading, police confirmed.
The attack took place at around 7pm in Forbury Gardens in the town centre, where police arrested 25-year-old Khairi Saadallah at the scene on suspicion of murder.
Police are not currently treating the incident as terror-related, but counter terrorism officers were called.
Detective chief superintendent Ian Hunter 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."
There was a initially a suggestion that the incident was being treated as terror-related but Hunter said terrorism was not being considered as the motive.
"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," he said.
Prime Minister Boris Johnson said his "thoughts are with all of those affected by the appalling incident in Reading".
"My thanks to the emergency services on the scene," he added.
Emergency air ambulances were called to the scene and five ambulance crews from South Central Ambulance Service attended.
Home Secretary Priti Patel tweeted to say she was "deeply concerned" about the incident.
Ms Patel later issued a statement condemning the stabbings as a "senseless attack on people simply enjoying a Saturday evening with family and friends".
Labour leader Sir Keir Starmer said the stabbing was "very concerning".
The leader of Reading Council, Jason Brock, said it was "an entirely senseless and horrific attack" in "a very busy area with lots of people socialising".
"I join residents across Reading in being shocked and appalled following the incident at Forbury Gardens," he said. "My immediate thoughts are with the families of all those who have died or have been injured.
Police and politicians have banded together to urge people not to share any footage of the Reading stabbing incident online.
While police have urged anyone with footage of the attack to come forward, they also stressed the importance of not posting any footage online out of respect for the victims' families.