One man has died and at least nine others have been injured in a spate of stabbings across parts of south London.
Police were called to four reports of stabbings in Croydon, Chislehurst and Wandsworth on Friday evening.
None of the stabbings are being linked by detectives, but Metropolitan Police said extra officers would be deployed in south London.
Det Supt Nicky Arrowsmith described the violence as “needless and completely abhorrent”.
The Met said none of the nine wounded were now considered to be in a life-threatening condition and added that two people had been arrested.
One of two men reported to have been injured at a property in Wisbeach Road, Croydon, was found dead at the scene just after 20:00 GMT.
A resident described seeing police and medical staff trying to save the 22-year-old man.
The witness, who asked not to be named, said: “There was blood everywhere, it looked like he was cut in the leg and they tried to stop the bleeding.
“His mum was here crying and she was in pieces.
“It is terrifying, my son is 19 and I’m worried for him.”
Homicide detectives have launched a murder investigation following the Wisbeach Road stabbing.
The other attacks are being investigated by officers from the South Area Basic Command Unit, the Met said.
These include a man who was stabbed on Chapman Road, Croydon, at 18:56 and four men who took themselves to hospital with stab wounds following a fight in the Penwortham Road area of Wandsworth.
Another two men, both in their 30s, also went to hospital after a stabbing on Jay Gardens, Chislehurst, just before 21:00.
Police are also investigating the stabbing of a man in his 40s who was found wounded on Dingwall Road at 21:12.
The victim has since been arrested on suspicion of affray and a 38-year-old man was arrested on suspicion of grievous bodily harm and remains in custody, the Met added.
Gold commander Ade Adelekan said: “While work continues to investigate the motivation and circumstances of these four incidents, I can say that they are being treated as isolated.
“However, that does not make this series of violent incidents any less shocking and I understand that residents in and around the areas where these incidents occurred will be rightly concerned.”
Labour MP for Croydon North Steve Reed said in a tweet that the “absolutely horrific news” would “devastate our community”.
18:56 – Two men stabbed on Chapman Road, Thornton Heath.
19:15 – Four men go to south London hospital with stab and slash injuries after fight in Penwortham Road, Wandsworth.
20:08 – Man fatally stabbed and another injured on Wisbeach Road, Thornton Heath.
20:51 – Two men go to south London hospital having been stabbed in Jay Gardens, Chislehurst.
21:12 – Man arrested on suspicion of grievous bodily harm after stabbing on Dingwall Road, central Croydon.