After another weekend of violence, officers announce new efforts to prevent knife crime, especially in London.
There have been 33 homicides in London this year and 24 of those were people killed with a knife
Four teenage boys have been arrested after two girls were stabbed in south London.
The boys, all aged between 16 and 17, have been arrested on suspicion of attempted murder and are in custody, police said.
Police were called to Norwood Road in Lambeth at 4.41pm on Sunday after reports of an assault.
The two girls, aged 16 and 17, were taken to hospital where one is in a serious but stable condition and the other has injuries that do not appear to be life-threatening.
Detective Sergeant Rob Merrett, of the Central South Command Unit, said: "This is a shocking incident involving two young female victims, one of whom remains seriously ill in hospital.
"It has understandably caused considerable alarm in the community.
"I urge anyone who has information, pictures and video that could assist us to make contact immediately."
Fares Maatou died after being stabbed in East Ham, Newham
On Friday afternoon, a 14-year-old - Fares Maatou - was stabbed to death outside a pizza restaurant in Newham, east London.
His death was the 33rd homicide in London this year and 24 of those victims were killed with a knife.
A 14-year-old boy has been charged with Fares's murder and a 15-year-old boy is in police custody, having been arrested on suspicion of murder during the weekend.
Another two boys, both aged 15, were also arrested over the killing and have been bailed until May.
It comes as police forces launch a week-long crackdown on knife crime - Operation Sceptre.
Officers will carry out weapons sweeps and people will be able to dispose of knives in amnesty bins across the country from Monday.
Londoners will be able to hand in knives at 12 police stations across the city.
People place flowers at the scene of the murder of 14-year-old Fares Maatou
The campaign will also see officers working with schools to discourage young people from carrying knives.
Metal detectors will be set up at transport hubs, along with drug detection dogs, the Met Police said.
National Police Chiefs' Council lead for knife crime, deputy assistant commissioner Graham McNulty, said: "Coronavirus has been a huge part of everyone's lives for over a year now but we want to remind people that our normal policing role hasn't stopped during this time.
"Forces are determined to tackle violent crime and with the restrictions easing, taking knives off our streets and helping people understand the dangers of carrying a knife remains a top priority."
Commander Alex Murray, the Met's violence lead, said: "This operation is an intensification of the work officers are already doing on a daily basis to tackle knife crime and remove dangerous weapons from the streets, and last year we saw a 26% reduction in violent crime across London.
"We are absolutely determined to keep violence levels down as we approach the summer months."
Source: Sky News