A 29-year-old man died after being stabbed in broad daylight following reports of a fight between two groups in west London.
Officers said the groups had dispersed by the time they arrived at the scene on Rosebery Road, Hounslow, on Monday afternoon.
The victim, who has not been named, was treated by paramedics but died at the scene just after 4.15pm.
The Metropolitan Police has launched a murder investigation and said inquiries are continuing.
No arrests have been made and police said a post-mortem examination is yet to be carried out.
Anyone with information is asked to call police on 0208 721 4054 or Crimestoppers anonymously on 0800 555111.