A 16-year-old boy has been stabbed and seriously injured in an attack by up to six people carrying knives in Deptford.
The attack took place on Saturday and left the victim in a critical condition in hospital.
One man has been arrested after an 18-year-old man was stabbed in Homerton High Street on Sunday afternoon.
Police said the fatal stabbing of a 30-year-old man in Camden on Sunday now meant three people were attacked with knives over the weekend.
Earlier this week, the Met said it was called to more than 9,000 knife crime incidents in London in the year ending April 2016.
'Open heart surgery'
There were 1,623 victims under the age of 25 including 866 teenagers, it said. Twelve were knifed to death.
In their campaign video Choose a life not a knife, people involved with the after-effects of knife crime, including a victim's father, police officer and a convicted murderer, all talk about the impact it has had.
Thomas Koing, a doctor at London's Air Ambulance service said 30% of the incidents they attended were due to knife crime.
"We see this almost every week, people being stabbed in the heart.
"We've had to change, we've had to up our game - we've had to do open heart surgery on the streets of London to try and save people's lives and that's hand-to-hand combat that belongs in war, it does not belong in London."
London Mayor Sadiq Khan said he was "extremely worried".
"We've got to make sure that we try and prevent young people from carrying knives in the first place. Every time a young person carries a knife is a sign of failure," he said.
To prevent this, he said more work was needed with schools and youth clubs to dissuade people from carrying knives and joining gangs.
He said there must be intelligence-led stop and search, and neighbourhood policing.
"I've spoken to the [Met Police] commissioner about this and he agrees with me, this has got to be one of our top priorities," he added.