The incident took place at Tarajuli tea estate in Assam's Sonitpur district on Thursday afternoon.
Police said the boy was sacrificed in the temple built by the tantrik Nanu Mirdha to perform puja.
"As per the eye witnesses statement, Mirdha lured the victim inside his temple and sacrificed him with a machete," police said, adding that later he came out of the temple and challenged the people to stop him.
"The incident came to focus after the boy remained missing for quite sometime yesterday (Thursday) forcing the family members to search for him. It was then they discovered Mirdha and the decapitated head of the boy near the temple," police said, adding that security personnel had been rushed to the area immediately but the mob lynched the tantrik to death.
"We are trying to ascertain if there is any enmity between the family of Mirdha and the victim," police said adding that the security has been intensified in and around the tea estate to ensure that the situation remains under control.
Congress leader and Deputy Speaker of the Assam Legislative Assembly Bhimananda Tanti on Friday expressed concern over the incident and said that it is a result of existing superstitions in the society, particularly among some of the tea tribe communities.
Tanti, who himself belongs to the tea tribe community, said that the government must take up urgent steps to spread awareness campaigns against these kinds of superstitions in the tea gardens of the state.