Police arrested a teenage boy on Friday over the knife murder of an 18-year-old male youth in south London, the 21st teenager to be killed violently in the capital this year, Scotland Yard said.
Officers arrested the 16-year-old at his home in Brixton in the early hours of the morning.
Police had been called on Thursday evening to reports of a fight in Guildford Road, south Lambeth, and found the 18-year-old stabbed in the abdomen.
He was taken to a nearby hospital where he was pronounced dead.
Police say they are aware of the victim's identity and have contacted his next of kin but are waiting for a formal identification before releasing further details.
Knife crime has become a top political issue in recent weeks with a spate of violent deaths, mostly stabbings, on the streets of London so far this year.
Official figures released on Thursday revealed there were more than 22,000 serious offences in England and Wales involving knives in 2007-8, although crime fell significantly overall.
