Four teenagers have been arrested over the murder of 16-year-old Ben Kinsella in north London, Scotland Yard said on Tuesday.
The four, all in their late teens, were being held at north and east London police stations after being arrested on Monday and early on Tuesday.
One was arrested in the Islington area, two at an address in Chadwell Heath, Romford, and the fourth in Bethnal Green.
Kinsella 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 in the early hours of Sunday.
Police said they had had a good response to their appeals for witnesses but called for more to come forward.
"We are still keen to speak to witnesses, in particular anyone who saw the stabbing itself, or anyone who has information about the identity of the suspects," said Detective Chief Inspector John Macdonald.
The victim's sister, former "EastEnders" actress Brooke Kinsella, appealed on Monday for an end to the violence that had claimed his life and that of 16 other teenagers in London this year.
Shocked friends and local people left wreaths, flags and candles by the roadside at the site of his murder.
On Tuesday, hundreds of people, many wearing T-shirts emblazoned with pictures of Kinsella and holding placards, took part in a protest led by the victim's family and friends through north London to the place where he was stabbed.
Kinsella's cousin Kate Whaley said young people needed protecting.
"The main message . is the knives have got to be put down, there's got to be an amnesty, there's got to be something like we had with the guns where we encourage young people to come forward and get rid of the knives," she told BBC TV.
"You don't need them. Something needs to be done to protect the good kids."
Two 16-year-old boys, who were arrested on Sunday following the attack, have been released on police bail.
