An 18-year-old Afghan refugee was fatally stabbed at Craneford Way Playing Fields in Twickenham in front of multiple witnesses on Tuesday.
The Metropolitan Police said they received calls at 4:45pm reporting the stabbing.
Hazrat Wali was pronounced dead at 5:54pm, police said.
Wali’s relatives have been made aware and are being supported by specialist officers.
At the time of writing, no arrests have been made.
“The incident occurred in a playing field area and was witnessed by a number of people, including groups that were playing football and coaching rugby at the time,” said Detective Chief Inspector Vicky Tunstall.
Tunstall said that some of the witnesses are believed to have taken videos of the incident, and appealed to the public not to share these publicly.
“I ask that any videos are not shared via social media to avoid causing the young man’s family any more distress at this already incredibly difficult time for them,” she said. “Instead, please go to the police immediately.”
Tunstall said the police were working to establish the motive and following leads. The police are asking anyone who may be able to assist with the investigation to reach out.
“Our thoughts are with the young victim and his family at this awful time,” said Chief Superintendent Elisabeth Chapple, commander for policing in south-west London. “If anyone has any concerns, or information that could help, I encourage them to contact those officers and tell us what they know.”
If anyone has information or footage regarding this incident, call the police at 101, or contact Crimestoppers anonymously on 0800 555 111.