Three men are in hospital after being found with stab wounds in Clapham.
Officers were called at 3.22am (June 15) to Bedford Road following reports of a fight.
Three men were found at the scene with stab and slash injuries.
The condition of two of the men is unknown, while the third has injuries which are not life-threatening or life-changing.
Four men were arrested in connection with the incident, two for violent disorder, one accused of carrying a bladed instrument and another for possession of a Taser, and have been taken into custody at a south London police station.
The news comes hours after two murders in Wandsworth and Greenwich, although they are not connected.
Metropolitan Police say fourteen people have been arrested in connection with the three incidents.
London mayor Sadiq Khan said he was "sickened" following the deaths of the two teenage boys.
Mr Khan said: "I am sickened to hear that two young lives have been ended within minutes of each other in Wandsworth and Greenwich.
"Our overstretched police are working around the clock to keep Londoners safe. They need our support to end this scourge of violence.
"Anybody who has information about what happened either in Wandsworth or Greenwich should do the right thing and call the police."
Tooting MP Rosena Allin-Khan said the suspected murder on Deeside Road was "heartbreaking" and "absolutely tragic".
"My heart goes out to the family of this victim after this absolutely tragic incident," she wrote on Twitter.
"I spoke at length with people on the Aboyne Estate tonight, anyone with concerns can contact me - I'm here to listen.
"Sending love to the Tooting family tonight - this is heartbreaking."
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