A teenage cyclist was attacked from behind and stabbed repeatedly by a man who fled in a car, police said.
Scotland Yard said the 17-year-old was found lying in a road in north-east London with multiple stab wounds in his arms, legs and back.
He was taken to hospital by paramedics, where he remains in a stable condition after the assault in Walthamstow on Thursday night.
Police said the suspect made off in a silver or grey vehicle towards Chingford Road after the attack at around 11.49 in Brookscroft Road near the junction with Kitchener Road.
A spokesman said: "At this early stage in the investigation it is believed that the victim was attacked from behind as he cycled along the street."
There have been no arrests, according to police.
Anyone who witnessed the incident or has any information is asked to contact DC Rob Bushell at Waltham Forest CID on 02032760968 or Crimestoppers anonymously on 0800 555 111.
