The child, identified as Afirul Islam, was playing at a house construction site when he slipped and fell into the pipe, official sources said.
Efforts were made for eight hours to rescue the child by digging around the side of the pipe by the State Disaster Response Force, Fire Brigade and Police, they said.
Afirul was brought out around 10.15 pm and immediately taken to Gauhati Medical Collge Hospital, where he was declared dead by doctors.
Oxygen was continuously supplied into the hole through a pipe for the child to breath in the hope that he was alive till the rescue operations were on, the sources said.