Former "EastEnders" actress Brooke Kinsella appealed on Monday for an end to the violence that has claimed the life of her brother Ben and 16 other teenagers in London this year.

Ben Kinsella, 16, was chased through the streets of north London and stabbed to death by up to four teenagers after a fight at a nightclub in the early hours of Sunday, police said.

"Now it truly is the time to stand up and put an end to this," Brooke Kinsella told a news conference. "Please, please let's learn from Ben and every other child that has been stolen from us.

"My family is determined to fight in his memory to make the streets safer for our children.

"Please, boys and girls, put down your knives and think about the pain and suffering they will cause."

Police said Kinsella was attacked after a fight at the Shillibeers pub and nightclub in Islington spilled out onto the street.

The teenager was chased down the road and attacked. Reports said he rang a friend to plead for help while running away.

One friend heard someone shout "Get him" before the attack, according to a report in the London Evening Standard newspaper.

Detective Superintendent Vic Rae, leading the investigation, said four black teenagers were believed to be involved in the stabbing.

"Witnesses saw the incident continue outside the club and up the road," he told reporters. "There are a number of other witnesses we would like to come forward."

Two 16-year-old boys, who were arrested on Sunday following the attack, have been released on police bail.

The deaths of so many teenagers have prompted police to launch a campaign to crack down on knife crime in the capital with an increase in stop and search operations.

Newly elected London Mayor Boris Johnson has also made tackling youth violence one of his priorities.