The deceased was identified as Moinur, 2, son of Mohammad Jabed. Mohammad Jabed, 35, his wife Sheuli Akter, 25 and their daughter Jannat, 4, sustained burn injuries.
Lima Akter, duty officer of the Fire Service and Civil Defence Control room, said the fire broke out on the ground floor of a two-storey building at Kasaituli around 8:15 am, leaving four members of the family injured.
Inspector Bachhu Mia, in-charge of Dhaka Medical College and Hospital police camp, said the injured were taken to the hospital in the morning where doctors declared the minor boy dead.
Dr Partha Shankar Pal, resident medical officer of Dhaka Medical College and Hospital, said Jannat received 60 percent burn injury while Sheuli 17 percent and Jabed 37 percent.
Fire service sources said the fire might have originated from gas leak.