Three men were stabbed and seven people arrested after a fight broke out in broad daylight near a tram stop in south London.
Scotland Yard said three males suffered stab injuries and were rushed to hospital. Their injuries are not life-threatening.
A fourth person suffered a serious head injury and remains in hospital.
A police spokesman added: "Seven males aged 15 to 19 were arrested near the scene on suspicion of GBH and taken to a south London police station where they remain in custody."
Local MP Sarah Jones tweeted: "I am in touch with police about this dreadful news. Anyone with any information should please report it to the police."
The tram stop was closed for several hours at the request of the police.
Detective Inspector David Willis said: “We have made seven arrests and we are pleased with how the investigation is progressing, but we are still appealing for witnesses to come forward.
“This incident took place in a busy area in broad daylight and we are sure there are people who witnessed the incident who have not yet spoken to us. It does not matter how insignificant you think the information you have is, I’d urge you to come forward.
“We are particularly keen to hear from anyone who has any mobile and/or dashcam footage of the incident itself as well as any footage of people congregating at the tram stop in Gravel Hill between 12.30pm and 1pm on Wednesday."
If you have any information about this incident, call 101 quoting 3199/20jan or Crimestoppers anonymously on 0800 555 111.
