A teenager was left with "serious" injuries after being stabbed in south London.
The man, in his late teens, was attacked in East Street, Walworth, at about 7.30pm on Tuesday.
He was taken to a south London hospital where he remains in a serious but stable condition, police said.
Witnesses said police sealed off the road for some time as forensics officers combed the area.
David Hayes, who lives nearby, said: "A couple of police cars sped past with sirens on my walk home.
"I got to East Street and the street was closed off with police tape. There were about 10 or more police cars there and at least one ambulance."
Scotland Yard said another male, of unknown age, has been arrested on suspicion of grievous bodily harm.
He remains in custody as officers continue to investigate.
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