The incident happened on Hotspur Street, Kennington, shortly before 16:30 BST.
The area’s Labour MP Florence Eshalomi appeared to suggest the victim was a boy.
In a post on X, formerly known as Twitter, she wrote: “Very sad to hear about the sad death of a young child who fell from a block of flats earlier this afternoon in Hotspur Street, SE11.
“My thoughts are with his family at this sad time.”
It comes days after a five-year-old child died in similar circumstances in east London.
The boy – who has been identified as Aalim Ahmed – fell from the kitchen window of a 15th storey flat in the Plaistow area.