Police are appealing for witnesses and information after a woman was stabbed in Edmonton.
Officers were called at approximately 7.02pm on Saturday to Aberdeen Road, north London, following reports of an assault.
London Ambulance Service also attended.
The victim, aged in her 40s, had sustained a stab wound to her back after being attacked by a man.
She has been taken to an east London hospital where she remains in a critical condition.
The suspect is described as a black man, approximately 6ft 3inches tall, of skinny build and wearing dark clothing, possibly a hooded top.
At this time there have been no arrests and a crime scene remains in place.
Enquiries continue to establish the circumstances of the incident.
Officers from the North Area Command Unit investigate and ask anyone with information to call 101 or tweet @MetCC, quote CAD6471/30Mar.
Alternatively contact Crimestoppers anonymously on 0800 555 111.
This incident is one of four stabbings in north London that have left four people in hospital, two of them in a critical condition.
Police are linking the attacks, which all took place in the Edmonton area between 7.02pm on Saturday and 9.43am on Sunday.
Investigators believe a single male suspect was acting alone, and may have mental health issues.
Acting Detective Chief Inspector Stuart Smillie from North Area Command said: “Police are treating the four stabbing related incidents as potentially linked. 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.”
A man was arrested in suspicion of GBH in Fore Street, Edmonton, at 10.53am on Sunday.
Smillie added: “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.
“Members of the public who have information about this suspect or have spotted someone acting suspiciously who matches his description are advised to call police on 999 and not to approach the man.
“His description has been circulated to all officers in North Area who are carrying out patrols, CCTV footage enquiries and policing busy areas around where the incidents took place, particularly where he was last seen where police arrived four minutes after the call to police was made.
“A picture of this suspect will be circulated as soon as one is retrieved. My advice to the public in the area where these incidents took place stay vigilant, beware of your surroundings and call 999 if you see anyone matching the suspects description behaving suspiciously.”