Four people have been stabbed to death during a string of apparently unrelated murders in London during a 24-hour period, police said.
Scotland Yard confirmed the male victims - a 17-year-old, 18-year-old and a 20-year-old on New Year’s Eve, and a 20-year-old in the early hours of Monday - all died as a result of their injuries.
A fifth man is in a critical condition after the New Year’s Day incident.
Five men have been arrested in connection with one of the deaths, the Metropolitan Police said.
Sunday’s stabbings took place in various locations across the capital - at 11.30am in Larmans Road, Enfield, 7.35pm at Memorial Avenue in West Ham, and 10.40pm in Norwood Road in Tulse Hill.
The New Year’s Day stabbing occurred at Bartholomew Court, Old Street, in the City.
Met Commander Neil Jerome said the incidents were not connected.
He added: “I am grateful to Londoners and visitors to the capital who co-operated with police - both at major celebrations in Westminster and at thousands of organised and private events across London - to enable the vast majority of people to enjoy New Year’s Eve.
“However, there were small groups who chose to engage in disorder and violence, and whose actions have had utterly tragic consequences.”
He added: “It is heart-breaking that, at a time when so many of us are contemplating what lies ahead in 2018, four families are dealing with the grief of losing a loved one to senseless violence and the callous use of knives as lethal weapons.
“I can assure Londoners - and the families and friends of the four males killed and the fifth who remains in hospital - that detectives will work tirelessly to bring to justice those responsible for such despicable acts of violence.
“As we begin these investigations and the provision of support to four grieving families, days like this serve to reinforce the determination of the Metropolitan Police to tackle knife crime and violence on our streets; especially offences committed by and against young people.
“I would urge anyone with information about these attacks, and more generally about anyone who routinely carries a knife, to urgently pass that information to police or Crimestoppers.
“If you’ve hesitated to do so before, then these four tragic deaths at the start of a new year may persuade you to act now to make London safer for your family and friends in 2018.”
Meanwhile, two men are critically ill after five people suffered stab or slash wounds in a fight at a Great Gatsby-themed New Year’s Eve party.
Police were called to Crystal Bar, on Carver Street in Sheffield, at around 2.20am on Monday following the altercation.
Two men were left with life-threatening injuries and remain in hospital in a critical but stable condition. Three other men suffered superficial injuries.