Four fire engines and around 25 firefighters attended a fire at a block of flats on Camberwell Church Street in Camberwell.
Most of a communal entrance and stairwell was damaged by fire. Four people were led to safety by firefighters from two flats. There were no reports of any injuries.
The Brigade was called at 0450 and Control Officers mobilised crews from Peckham, Brixton, Old Kent Road and New Cross fire stations to the scene. The fire was extinguished by 0553.
The cause of the fire is under investigation.