A 15-year-old boy was chased and stabbed to death during a row between two groups of youths, police have said.
Sunday Essiet was found with stab wounds in Invermore Place, Woolwich, south-east London, on Tuesday.
He was with friends in a fenced-off football pitch on the Glyndon estate when it is thought they were approached by another group of youths.
Police said a row broke out and Sunday was chased to the edge of the green where he was caught and attacked.
Sunday, who was pronounced dead at the scene, is the fifth teenager to be killed in London this year.
2008 TEENAGE LONDON MURDERS
1 January: Henry Bolombi, 18, stabbed to death
5 January: Faridon Alizada, 18, stabbed to death
21 January: Boduka Mudianga, 18, stabbed to death
26 January: Fuad Buraleh, 19, beaten to death
19 February: Sunday Essiet, 15, stabbed to death
Det Supt Phil Adams said: "This incident has taken place in the middle of an estate, with a number of properties overlooking not only the initial incident but the subsequent fatal assault.
"I am pleased to say that we have already had a large number of people from the local community come forward, but we would still like to hear from anyone who witnessed the incident or who has information."
A post-mortem examination was due to be carried out on Wednesday.