A 20-year-old man was stabbed 10 times in a London street in the latest incident of knife violence in the capital.
He suffered significant blood loss, but survived the "vicious, unprovoked attack", carried out late on Tuesday night, with non-life-threatening injuries, police said.
It is the latest in a string of stabbings involving young men, coming days after four people, including two teenagers, were stabbed to death in unrelated attacks across the city in the space of 24 hours.
The 20-year-old was chased by a group of teenagers, then ambushed and repeatedly stabbed as he knocked on a door of a residential street in Harrow, northwest London, for help.
The Metropolitan Police described the suspects as a group of black males in their late teens, who were wearing dark clothing, and appealed for witnesses to the attack in Eastway Crescent to come forward.
Detective Sergeant Amar Patel said: "This was a vicious unprovoked attack on a young male who had been enjoying an evening with friends when he was chased, ambushed and repeatedly stabbed by a group of males for an unknown reason.
"We have already spoken to lots of people in the area about the incident, but I would appeal to anyone who witnessed the attack and hasn't spoken to us about it yet to come forward.
"Any detail, no matter how insignificant it may seem, will help us to identify those responsible and bring them to justice."
A 17-year-old boy and two men, aged 18 and 20, attacked on New Year's Eve, along with a 20-year-old man knifed in the early hours of the following morning, all died as a result of their injuries, while a further victim was left critically ill in hospital.
Sunday's stabbings, at 11.30am in Larmans Road, Enfield, 7.35pm at Memorial Avenue in West Ham, east London, and 10.40pm in Norwood Road in Tulse Hill, south London, took the number of people stabbed to death in the capital last year to 80, Scotland Yard confirmed.
Of those, 18 involved victims under the age of 19.
A 19-year-old man has been arrested on suspicion of murder over the New Year's Day stabbing at a house party in Islington, north London, while five males, aged between 17 and 21, have been arrested in connection with the Enfield attack.