Three people are feared dead and several have been taken to hospital after being stabbed in a serious incident in a park in Reading.
Police were called to Forbury Gardens at about 19:00 BST following reports of a stabbing. They have not yet confirmed the number of dead and injured.
Thames Valley Police said a man was arrested at the scene and is now in custody.
There are reports that a police officer “rugby tackled” a suspect to the ground, according to the Sunday Mirror.
Armed police officers with shields were later seen entering a block of flats in Basingstoke Road in Reading, and families living in the building have been moved out.
Police and Black Lives Matter organisers have said the incident was unrelated to a protest held earlier in the park.
South Central Ambulance Service said “multiple ambulance resources” were sent to the scene, including five ambulance crews and a helicopter.
“We were assessing and treating a number of casualties who had sustained injuries as a result of the incident,” the service said in a statement.
What do we know about the suspect?
Security sources have told the BBC the man arrested at the scene is thought to be Libyan, and counter terrorism officers are at the scene.
Police have not ruled out terror as a possible motivation for the attack.
What did witnesses see?
Eyewitness Laurence Wort, 20, told the BBC that he was visiting Reading for the day and was about 10m from the attack.
“A man walked along the path opposite where we were walking past a group of eight to 10 men, before darting to the left and going to stab three people in the first group,” Mr Wort said.
“Changing direction, he runs towards us and then when we realises he’s not going to catch us, he turned back and went for another group that hadn’t realised what was happening yet, and he managed to stab someone in the second group,” he said.
Claire Gould, a freelance journalist who lives in Reading, said she walked past Forbury Gardens at around 18:40 BST “and everything seemed calm”.
She then saw an air ambulance land in King’s Meadow – another park close to the scene – at around 19:00 BST, followed by a second around 10 minutes later.
“There were multiple sirens from 19:00 going on for the next couple of hours and police helicopters [were] circling,” she added.
What has the reaction been?
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.
Home Secretary Priti Patel tweeted to say she was “deeply concerned” at the incident.
She said: “My thoughts are with everyone involved, including police and emergency responders at the scene.”
Policing minister Kit Malthouse has described the incident as “horrific” and “dreadful”.
Labour leader Sir Keir Starmer said the stabbing was “very concerning”.