Four unrelated fatal stabbings which took place across London during the New Year period were “truly unusual and extraordinary”, the deputy commissioner for the Metropolitan Police has said.

Murder investigations were launched after a 20-year-old man died after being stabbed in Memorial Avenue, West Ham, shortly after 7.30pm on New Year’s Eve, while a 17-year-old boy died after being stabbed in Tulse Hill three hours later.

An 18-year-old died in hospital after being stabbed in Enfield at 11.30am the same day, while a 20-year-old man died after being stabbed at a house party in Old Street, Islington, in the early hours of New Year’s Day.

Six males have been arrested as a result of two of the attacks.

Deputy Commissioner Craig Mackey said his thoughts were “with the family and friends of those affected”.

“The reasons behind it are quite complex. There are a number of issues affecting knife crime,” he said.

“We are absolutely clear we are doing our part to do the things we can do as the police service... but we need others across London working with us to help tackle those underlying issues around a knife culture that has emerged across London.”

He added: “I’m not here today to ask for or bid for more resources, we’d always like more resources in terms of those things we tackle.

“But it’s clear there are things we can do at the moment collectively that will help around knife crime.”

Scotland Yard said a 19-year-old man has been arrested on suspicion of murder over the Islington stabbing while five males, aged between 17 and 21, have been arrested in connection with the Enfield death.

Nobody has yet been arrested over the West Ham or Tulse Hill incidents.