Four men are in hospital after one was shot in Brent, north London, and others were stabbed.
One arrest has been made, and the men are said to be in a critical condition.
The first incident was around 8.10pm yesterday evening.
“Police and the London Air Ambulance were alerted after a 23-year-old man was found with stab injuries in Creek Road, Deptford, in south-east London, at about 8.10pm.
He is being treated in a south London hospital,” the Metropolitan Police said in a statement.
The shooting, which reportedly involved a machine gun, took place in Brent around 25 minutes later.
The Metropolitan Police said: "Police were called by the London Ambulance Service at approximately 8.34pm to reports of a man with gunshot injuries on Lawrence Avenue in Brent.
"Officers attended. A man believed to be aged in his 20s has been taken to a central London hospital with life-threatening injuries."
Police were then called to the scene of the stabbing almost two hours later.
"Police were called at approximately 10.19pm to reports of a stabbing on Rainborough Close, NW10,” said a statement.
“A male, aged in his 20's, was found with stab wounds. He has been conveyed to a London hospital with life-threatening injuries.
“He remains in a critical but stable condition."
An investigation has also opened after a man, believed to be 30 years old, was found with stab injuries in the Old Kent Road, south-east London. He is being treated at a south London hospital.
Police were called to the scene by the London Ambulance Service at approximately 3.36am on Friday.
Scotland Yard said that a man, believed to be aged 28, was arrested at the scene on suspicion of grievous bodily harm. Roads are cordoned off.
There have been 61 murders in London this year, with nine of those fatal shootings.
London Mayor Sadiq Khan called for police to be “confident” in using targeted stop-and-search in London to try and fight the crime wave.
Former police officer Norman Brennan told talkRADIO in April that cuts to the number of officers meant the force was struggling to cope with increasing crime.
Extra stop-and-search powers will be in effect in the areas today.