A teenage boy has been stabbed to death in central London.
The Metropolitan Police said the attack happened at about 18:50 GMT on Sunday in the Lupus Street area of Pimlico.
The boy, believed to be aged 16, was taken to a south London but died two hours later.
Officers said they were treating his death as murder and said no arrests had yet been made. Lupus Street has been closed while investigations take place.
A police spokesman said they would "retain an open mind" about the circumstances and motives of the attack.
'Reeling and swaying'
A 22-year-old resident of a block of flats overlooking the murder scene, said: "I came outside just seconds after it happened because I heard a lot of commotion and the victim was shouting.
"I came outside and saw the victim standing and holding his stomach and about three or four young blokes running down the street opposite.
"He was reeling and swaying for about 20 seconds and then fell and then people started gathering and calling the ambulance."
He added: "I am surprised that this has happened right on my front doorstep. I always had the impression that Pimlico was a quiet and affluent area."
Councillor Nickie Aiken, from Westminster City Council, said the murder would be top of the agenda when she met Metropolitan Commissioner Sir Bernard Hogan-Howe later.
"Once more we have seen the tragic blight that knife culture has inflicted on the capital," she said.
"Our thoughts are with the family of this teenager and we will offer whatever help we can."