The latest victim, who has not yet been named, died in busy Upper Street, Islington, in broad daylight at around 6.30pm on Monday.
Police have put up a cordon along the road, which has shops and restaurants and is known for its nightlife.
Officers have begun a murder investigation and have appealed for anyone with information to come forward.
CCTV footage has emerged appearing to show a street scene around the moment the fatal stabbing took place in north London.
The attack was witnessed by several members of the public, including a young girl.
Moments later a man was seen fleeing from the scene in Upper Street.
It is not known if he is connected with the incident.
Business owner Gregory Barry said he saw the incident unfold over his CCTV.
He said: “There were two blokes in a van, it pulled up on the street. It looked like there was an altercation and the fight carried on outside the van.”
No arrests have yet been made in connection with the fatal stabbing.
Islington councillor Paul Convery described the assault as “horrifying”.
He tweeted: “Shocking incident on Upper Street right now outside Town Hall. Reported that man fatally stabbed.”
Meanwhile, police have charged a suspect with murder following the fatal stabbing of a man in south London on Sunday.
Manimaran Selliah, 44, of Mitcham, has been charged with the murder of 28-year-old Arunesh Thangarajah in Mitcham.
Selliah has also been charged with the attempted grievous bodily harm of a 35-year-old man.
He has been remanded in custody to appear at Wimbledon Magistrates’ Court on Tuesday.
Officers continue to appeal for information and witnesses to the attack.
Detective Chief Inspector Simon Harding said: “We will be speaking to locals and continue to appeal for those who witnessed the attack or have information to get in touch.
“I fully appreciate the alarm this incident has caused within the area.
“This attack is not being treated as gang-related or racially motivated. The local community can expect to see my team in and around the area as the investigation continues apace.
“I would encourage anyone with concerns to speak with officers or contact their local neighbourhood policing teams.”