They need stricter knife control laws there.
Two teenagers and a man in his 30s have been killed after five separate attacks in London over a 24-hour period.
Police have arrested a total of 14 people following the unlinked attacks in east and south London in a wave of violence that began on Friday afternoon.
None of the attacks is believed to be linked, but the pressure of dealing with so many incidents has put Metropolitan police officers under pressure, Sadiq Khan, London’s mayor, has said.
He expressed his disgust and said the force was working at its limit. “I am sickened to hear that two young lives have been ended within minutes of each other … Our overstretched police are working around the clock to keep Londoners safe. They need our support to end this scourge of violence.”
Donald Trump, the US president, used the murders to attack Khan, renewing the antipathy between the two men. He retweeted a post by hard-right commentator Katie Hopkins about the killings, saying: “LONDON needs a new mayor ASAP. Khan is a disaster – will only get worse!”
A spokesman for the mayor said he was “focusing on supporting London’s communities” and was “not going to waste his time responding to this sort of tweet”.
The first attack happened at 4.42pm on Friday in Wandsworth, south-west London, when an 18-year-old was stabbed in Deeside Road. Six males aged between 16 and 19 were arrested on suspicion of murder.
Just 12 minutes later, a 19-year-old man was shot dead in Plumstead, in the south-east of the capital , 13 miles away. Police have arrested three boys aged between 16 and 17, and a 17-year-old girl on suspicion of murder.
Then, at 3.22am on Saturday, two men were slashed and stabbed in a fight near Clapham North underground station. Four men were arrested, two for violent disorder, one for carrying a bladed instrument and another for possession of a stun gun.
The fourth attack happened at 4am, after a fight at a pub in Brixton, where one man was stabbed and injured.
Then just before 2pm a man in his 30s was stabbed to death in Alton Street, Tower Hamlets, in a field near a nursery and a mosque.
Scotland Yard said residents in both areas could expect to see a heightened police presence as detectives from the Met’s homicide and major crime command investigated.