Two teenagers were stabbed to death in London's bloodiest day of gang violence this year.
A 14-year-old was killed on his way home from school and a 17-year-old was stabbed to death after a dispute apparently started on a bus.
The killings of Amro Elbadawi, 14, in West Kilburn and Devoe Roach, 17, in Stamford Hill, were being treated as "gang-related" by police.
The deaths, which bring to 11 the number of teenagers killed in violence this year, came on the day Mayor Ken Livingstone launched his manifesto for tackling crime.
Mr Livingstone was appearing at Kilburn police station, a quarter of a mile from the scene of Amro's death. He was facing growing criticism for accusing the media of over-hyping violent crime and ignoring falls in other crimes, by saying "if it bleeds, it leads".
Detectives investigating Amro's death are looking into claims that it stemmed from a gang dispute in the playground of the Paddington Academy in Maida Vale. (NWN: Our emphasis. A playground ?).
Amro was attacked at 5.15pm in Dart Street, West Kilburn. Bleeding badly, he staggered into a health centre where doctors tried to revive him. He died an hour later in St Mary's Hospital, Paddington.
The boy, whose parents are Egyptian, was described on tribute websites today as a member of gang on the Mozart estate, where he lived with six siblings.
On MySpace, he was named as part of the SD Crew, whose initials were said to stand for "Street Dreamz/Street Disciples/Secret Dealers". The gang claims to consist of 50 "soldiers" and "yungas" - younger members.
Fellow members posted tributes, saying: "RIP Amro, I love you to bits, I won't 4get u I love u Amro, rest in peace bro, I will neva forget you."
Parents claimed a feud had been building at the academy for a week. "The atmosphere was like a pressure cooker," said one, who did not want to be named.
"Every day my son came home saying there was talk that someone was going to be stabbed in a big fight.
"Amro has two brothers and I'm worried about what will happen in the playground today."
Last night police sealed off a park in the neighbouring Queens Park Estate and arrested a 16-year-old boy. He was being questioned on suspicion of murder today.
A post-mortem examination was taking place at Westminster mortuary. Detective Chief Inspector Andy Mortimer who is leading the investigation said: "I would urge anyone who may have information to come forward."
Amro's death came just seven hours after Devoe, 17, was stabbed to death in Tottenham High Road, Stamford Hill, as he went on an errand with a friend.
The teenager from Stoke Newington, who attended Hackney Community College, was stabbed in the chest outside the Turnpike House pub.
Charles Quagraine, 45, a family friend, said: "They went to the shops and these boys asked Devoe what he was looking at. He was stabbed because someone thought he was looking at them, it's as stupid as that."
The killer fled up Ravensdale Road. Paramedics operated on Devoe in the street and he was taken to the Royal London Hospital in Whitechapel but died about an hour later. He lived just a few streets away with his mother, Dionne.
No arrests have been made.