A 17-year-old boy has died after being stabbed outside Clapham South Tube station in south London.
It comes less than 24 hours after a 15-year-old boy was also stabbed to death in southeast London.
Police were called at approximately 4.35pm on 2 November to reports of a stabbing outside Clapham South Tube Station.
The teenager was pronounced dead in hospital at 5.23pm.
His next of kin have not been informed and no arrests have been made at this stage.
A passer-by, Robin Pritchard, tweeted he saw "some poor kid on the floor in a pool of blood, police doing CPR".
The charity director, 47, told reporters: "I saw the guy on the floor, a pool of blood like he'd been stabbed in the stomach, his clothes were soaked.
"It was strangely calm and quiet. I think everyone was in shock. Lots of kids there from the local college.
"All I really registered were grey tracksuit bottoms which were soaked with a pool of blood coming from his waist like he'd been stabbed in the stomach."
Roads around the Tube station have been closed with police remaining on scene.
An hour after officers were called, British Transport Police tweeted to say the "station is currently closed and may be for some time".
They urged people to avoid the area.
Those travelling on the Tube going through Clapham South were told police had shut the station.
On Thursday evening a 15-year-old described by neighbours as a "sweet boy" was stabbed to death on the streets of London.
The victim, named locally as Jai Sewell, was taken to hospital with stab wounds following an incident in Randlesdown Road in Bellingham, southeast London, and was pronounced dead at 8.15pm.
The teenager wanted to become a cartoonist and loved riding his mountain bike, his aunt told the Evening Standard.
Rochelle, 32, said her nephew was not involved in gangs, adding: "He said he was going out to get some food and he never came back."
She said: "He loved riding his mountain bike, was very bright and brilliant at art. He wanted to be a cartoonist."
Local Dionne Wright, 36, said she used to see Jai on the bus every day and rushed to chicken shop Morley's when she heard about the incident.
She said: "I saw him, he was on the floor, I saw him lying there."
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Ms Wright said that the victim and his friends used to "congregate" around Morley's every day, but "something like this hasn't happened before".
She added: "I just know he was a sweet little boy."