Police said 14 people were arrested over the three incidents, two of which saw a pair of teenagers lose their lives just 12 minutes apart.
“I am sickened to hear that two young lives have been ended within minutes of each other in Wandsworth & Greenwich,” tweeted Sadiq Khan, who has seen knife crime increase in virtually every borough of the city.
Police were first called to Wandsworth, southwest London at 4.42 p.m. local time (11.42 a.m. ET) on Friday, after an 18-year-old victim was stabbed. He died at the scene, and six males — all aged between 16 and 19 — were arrested.
Then, at 4.54 p.m., armed police were called to reports of a shooting in Woolwich, south-east London, where a 19-year-old had been shot. He also died at the scene, before three boys and a girl, all aged 16 or 17, were arrested on suspicion of murder.
Finally, at 3.22 a.m. on Saturday morning, three men were stabbed in Clapham, south London, and four other men were arrested.
The number of young individuals admitted to hospital with wounds inflicted by knives or sharp objects in England has soared by more than half in the past five years, the NHS has said.
Police recorded a total of 40,577 offenses involving a knife or sharp instrument across the country in 2018, 10,000 more than in 2010-11. Shootings, by contrast, are far more rare in the UK.
Khan joined police in appealing for information on the latest attacks. The Mayor has faced criticism for the rises in violence in recent years, while others have pointed the figure at police cuts mandated by the government.
“Our overstretched police are working around the clock to keep Londoners safe,” Khan said. “They need our support to end this scourge of violence.”