The seven-year-old, named as Joel Urhie by his father John Uhrie, lost his life in a blaze at a house on Adolphus Street in Deptford.
Speaking to reporters at the scene, he said: "It's terrible, the pain we cannot forget."
Vicar of nearby St Nicholas Church, Rev Louise Codrington-Marshall told Premier: "Obviously, we're all shocked and grieved at this sad news and our thoughts and prayers are with the family at this time.
"We'll be praying for them at church and lighting candles and supporting the family the best we can."
The fire was first reported to emergency services at 3.25am on Tuesday.
Neighbours described hearing screams from the property.
Two women were taken to hospital with non-threatening injuries after jumping from a first floor window.
Rev Codrington-Marshall added: "I've spoken to one of my parishioners who lives along that street.
"She said she was out until 3am, lots of people were shouting and trying to assist. The fire was too great so they had to wait for the fire brigade in the end."
Around 35 firefighters and six engines responded to the blaze, which was brought under control by 4.50am.
Treating the fire as suspicious, the Metropolitan Police has launched an arson investigation.
No arrests have been made.
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