Police yesterday arrested a teenage boy 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.

Factbox - London teenage murders

Twenty-one teenagers have been murdered in London so far this year as the capital remains grimly on track to match last year's record of 26 shooting or stabbing fatalities among young people.

Below are the details of this year's victims:

1. Henry Bolombi, 17, was stabbed once in the chest on New Year's Day as he got off the 279 bus near his home in Edmonton, north London, after seeing in the festivities in central London.

2. Faridon Alizada, 18, from Bexley, southeast London, was stabbed three times in the chest on January 5 during a fight in a tower block on a council estate in nearby Erith.

3. Boduka "Louis" Mudianga, 18, was stabbed to death during a street fight near his home in Edmonton on January 21.

4. Fuad Buraleh, 19, from Hayes, Middlesex, was beaten about the head with a blunt instrument during a row in a West Ealing park following a night out on January 26. He died in hospital less than an hour later.

5. Nigerian-born Sunday Essiet, 15, from Southwark, southeast London was "kicked like a football" and stabbed by a gang of six youths on a nearby Woolwich estate on February 19.

6. Tung Le, 17, from Deptford was stabbed during a fight near Trafalgar Square on February 23 after a night out in the West End. The Vietnamese teenager died in hospital six days later.

7. Ofiyke "Iyke" Nmezu, 16, from Edmonton, died from a fractured skull after being beaten across the head with a brick during an attack in Enfield, north London. He died in hospital a fortnight after the attack on February 1.

8. Michael Jones, 18, was stabbed to death after being attacked by an intruder at his home in on March 13. He died from serious head injuries after he was found by his mother, Kathleen, tied to a chair in his Edmonton home.

9. Nicholas Clarke, 19, from Brixton, south London, was shot dead on a nearby housing estate on March 14.

10. Devoe Roach, 17, from Stoke Newington, north London, was fatally stabbed through the heart during a row on a busy shopping street in Stamford Hill, north London on March 27.

11. Egyptian-born Amro Elbadawi, 14, from West Kilburn in west London, died from a single stab wound to the throat during a knife fight with a 16-year-old on an estate in Queen's Park, West London on March 27.

12. Lyle Tulloch, 15, of Peckham was stabbed to death in a block of flats in Southwark on May 3 - just hours after Boris Johnson was elected Mayor of the capital. The assault happened less than a mile from where 10 year-old Damilola Taylor was killed with a broken bottle in 2000.

13. Jimmy Mizen, a teenager of "immaculate character", bled to death after a frenzied attack in Lee, southeast London, on May 10 - the day after his 16th birthday. He died in his older brother's arms, his throat slashed by a shard of glass, after the unprovoked fight with a youth who had smashed his way into a baker's shop near his home.

14. Actor Rob Knox was stabbed during a fight outside a pub in Sidcup, Kent, on May 24, that left three of his friends with serious knife wounds. The 18-year-old had a small part in the forthcoming film Harry Potter And The Half-Blood Prince.

15. Sharmaarke Hassan, 17, was shot in the head in a Camden Street on May 24 and died in hospital four days later.

16. Arsema Dawit, 15, was found on June 3 with multiple stab wounds in the lift of the block of flats where she lived near Waterloo Station.

17. Ben Kinsella, 16, was chased down a street in north Islington and stabbed to death by up to four teenagers after a fight at the Shillibeers pub and nightclub early on June 29.

18. Shakilus Townsend, 16, died in hospital on July 4 after being attacked with a baseball bat and stabbed in Thornton Heath, south London.

19. David Idowu, 14, died in hospital on July 7, nearly three weeks after being stabbed in Great Dover Street, Borough, south London.

20. Melvin Bryan, 18, died on July 10 from stab wounds to his neck and chest after a fight in Gloucester Road, Edmonton.

21. Unnamed 18-year-old male, died on July 17 after being found in south Lambeth, south London, with a stab wound to his abdomen.