The youths had pulled up their hoods and covered their faces in bandanas for the planned attack.

They also want to trace a black girl, aged in her mid-teens and wearing a floral dress, who stood back with up to eight others and watched the sickening attack.

Police have recovered two knives, one of which was described by a witness as 18in long.

The death brings the toll of teenagers killed in knife attacks in the capital this year to 18.

The detective leading the investigation said it was "another senseless incident in which a young life has been taken away by a knife".

Shakilus' death came as three teenagers appeared in court in the north of the city accused of stabbing 16-year-old Ben Kinsella to death at the weekend.

Police are also continuing to investigate fatal knife attacks on Tunisian Hamouda Bessaad, 34, in Old Kent Road on Monday, and Dee Willis, 28, in Peckham on Tuesday.

Metropolitan Police Deputy Commissioner Paul Stephenson emphasised that tackling knife crime was the force's "number one priority".

Speaking at a Metropolitan Police Authority meeting, he said the officers would be deployed to the worst affected of London's 32 boroughs "with immediate effect".

Teams of officers have already been sent to trouble hotspots since the launch of Operation Blunt 2 in May.

Armed with wands and knife arches, the officers have been carrying out searches using powers under Section 60 of the Public Order Act, which allows them to operate under the presumption of reasonable suspicion.

London's deputy mayor for policing, Kit Malthouse, said: "Eighteen young people dead in six months is completely unacceptable and we will do everything in our power, in the short term, to bear down on the immediate problem, while recognising that the ultimate solution lies in more complex and longer-term interventions that turn the faces of our children away from a life of violence."