Clad in black and armed with knives and belts, the clip shows at least three assailants whipping, punching and kicking several apparently defenceless victims.
As the blows rain down one of the attackers can then be seen drawing a knife and thrusting it forward while holding a mobile in his other hand.
A teenager has been left needing surgery after being stabbed repeatedly in a takeaway by masked thug
This is a shocking and brutal assault that has left the victim very distressed from his ordeal
The teenager suffered four stab wounds to his leg, one to the abdomen and one to the arm in the attack that took place on Monday evening.
Police said they were called to the Dallas Chicken takeaway on Brixton Road at 5.30pm.
Dressed in black and armed with knives and belts, at least three assailants attacked their victims
The attack was filmed on a mobile phone
Detective Constable Remy Smith, from Lambeth CID, said: “This is a shocking and brutal assault that has left the victim very distressed from his ordeal. We are keen to identify the men in the CCTV footage so we can speak to them about the incident. We would also urge anyone who witnessed the incident to contact us.”
According to witnesses there were a further three suspects on bicycles outside the shop at the time of the assault. All of the suspects then left together as a group as they made their way northbound along Brixton Road.
One man was later arrested on suspicion of possession of a knife and police appealed for help in finding four other suspects.
One is described as a black man, aged in his early 20s, of medium build. He was wearing a black puffa-style jacket, blue jeans, a white belt, a black face-covering and black shoes with white laces.
The teenager, who has not been identified, was hit in the face with a belt and stabbed several times
The police are keen to identify the men in the CCTV footage
A third is also as black, slim and aged in his early 20s. He was wearing a black jacket, dark trousers, black gloves, a black face-covering and black shoes. He was seen to carry a knife.
A fourth is also black and slim, aged in his early 20s. He was wearing a black jacket, dark trousers, black gloves, a black face-covering and black shoes.