The victim, whose age and condition is not known, was found by paramedics suffering “stab and slash injuries” in Westbury Avenue, Turnpike Lane at 12.50pm on Monday.
A resident said they saw the air ambulance circling above Turnpike Lane waiting for a space to land to treat the victim.
They added: “The officer on the cordon confirmed that the stabbing happened elsewhere and the victim made it to the parade of shops on Westbury Avenue before collapsing.”
“Officers attended. A man was found suffering from stab and slash injuries.
“Emergency services remain in attendance.
“There have been no arrests.”