3 dead in stabbing at UK park; 1 person in custody

Three people were killed in a stabbing attack Saturday night in a park in Reading, England, police said.

Thames Valley Police wrote on Twitter the "incident" happened at Forbury Gardens in Reading, about 40 miles west of downtown London.

In addition to the three people who were killed in the attack, three others were injured.

"The Thames Valley Police Major Crime Unit has launched a murder investigation following this incident," Thames Valley Detective Chief Superintendent Ian Hunter, said in a statement. "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," he added.

A 25-year-old man was arrested on the scene, Thames Valley Police said.

Police said the stabbing was "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," authorities said.

Officers were on the scene and investigating. Forbury Gardens was cordoned off and police asked people to avoid the scene.

Authorities also urged people not to share video of the incident on social media, and instead contact police.

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."

A protest against racism took place in the park earlier on Saturday, but Thames Valley Police said there was no reason to believe the stabbing was connected.

ABC News' Mike Trew and Matt Foster contributed to this report.