At 1.27am on Sunday, 13 June, officers were called to a disturbance and reports of shots fired in Ridgway Road, SW9.
Officers attended along with London Ambulance Service (LAS) colleagues and found a 32-year-old man suffering stab injuries.
He has been taken to hospital where his condition has been assessed as potentially life-threatening. The victim had also sustained shotgun pellet injuries to his legs.
Three other males and two females also attended hospital with shotgun pellet injuries, primarily to their legs. None is in a life-threatening condition.
Four of these five self-presented at hospital and a fifth was taken to hospital by LAS from a location elsewhere in Lambeth at around 3.40am.
Enquiries are under way to establish the circumstances. There has been no arrest at this early stage.
A Section 60 order has been authorised which will remain in place until 2.30pm on 13 June, covering much of the London Borough of Lambeth. Met officers will be working across the borough to help keep people safe.
Anyone with information that may assist police is asked to call 101, ref 918/13jun. To remain anonymous, please contact Crimestoppers.
Hard calls save lives. Are you close to someone on the fringes of knife crime? Do the right thing, please give information 100 per cent anonymously through the independent charity Crimestoppers. It can feel like a hard call, but it could save the life of someone you love.
No piece of information about knife crime is insignificant or too small. Any information you give to Crimestoppers can make a difference in reducing knife crime and the harm it causes to families.
They never ask your name and they cannot trace your call, your IP address or the device you use. Fill in their quick online form or call 0800 555 111. It could save a life.