A young man is in hospital with a stab wound after an altercation near Elephant & Castle on Monday evening.
The victim was given first aid by police officers whilst an ambulance was on its way.
The young man was taken by ambulance to an east London hospital suffering a stab wound. His condition is described as serious but stable.
Detectives from Southwark CID are carrying out inquiries into the incident.
A Metropolitan Police spokeswoman said that detectives believe that the victim was stabbed following an altercation on a bus in London Road which spilled out onto the street.
Any witnesses or anyone with any information can call police on 0300 123 1212; if you wish to remain anonymous please call Crimestoppers anonymously on 0800 555 111.
Two males were arrested at the scene in connection with the incident and are currently in custody at a south London police station.