There has been a heavy police presence in north London overnight following a spate of random stabbings, as police continue a major manhunt.
A knifeman stabbed four people in the back in separate attacks, leaving two in a critical condition.
Two men are being held on suspicion of grievous bodily harm but police have warned the investigation is “live” and members of the public should “remain vigilant”.
Police are continuing to search the Edmonton area and were seen patrolling the streets in cars and on foot throughout Sunday evening.
The attacker is believed to be a single male who is described as black, about 6ft 3in, of skinny build and wearing dark clothing, possibly a hooded top.
A man was arrested shortly before 11am on Sunday in Edmonton and another man, in his 40s, was later arrested at a residential address in the same town. Both suspects remain in custody.
Following the second arrest, the Met Police said in a statement: “This remains a live investigation and police are pursuing all lines of inquiry.
“Members of the public are advised to remain vigilant and to report anything suspicious to police.”
Police say all four victims were attacked from behind as they were walking alone.
The first victim was a 45-year-old woman who was stabbed in the back in Aberdeen Road at about 7pm on Saturday and remains in a critical condition in hospital.
A 23-year-old man who was attacked near Seven Sisters tube station shortly before 4am on Sunday is also in a critical condition.
Two more victims were stabbed in Park Avenue and Brettenham Road, but their injuries are not believed to be life-threatening.
Acting Detective Chief Inspector Stuart Smillie said police are doing everything they can to “apprehend the suspect behind these cowardly and senseless attacks”.
He added: “We believe the culprit knows Edmonton and may well be from the area.
“The motive for the stabbing appears to be solely to inflict harm.”
“The four victims are all from different backgrounds and appear to have been selected at random due to them being alone and vulnerable. There is nothing to suggest this incident is terror related.
“We are working on the hypothesis that the single male suspect is acting alone and mental health issues may be a factor.
“All of the people he has targeted have been walking alone and he has approached from behind without warning.”
Dervish Husseyin, 60, witnessed the aftermath of the first stabbing while he was visiting a friend’s house in Aberdeen Road.
“I seen the woman lying down, face down,” he said.
Mr Husseyin said the woman had “blood on her back” but seemed unaware she had been stabbed, saying she had been “beaten up”.
“She said she only went out for a walk on her own,” he added.
He said a man who claimed to have witnessed the attack described seeing two black men.
Natasha Cameron, 45, lives in Aberdeen Road and was walking home from work at a nearby casino after 10pm.
She was told there had been a stabbing by officers but was unaware of the later attacks.
“I’m scared now because I always walk here from work home,” Ms Cameron said.
“Now I’m definitely taking the bus.”