The child, an orphan, was adopted by fisherman N Ramana and his wife Kalyani, of Chinnaganjam village in Prakasam, about two years back, police sub-inspector B Narasimha Rao said.
However, a proper procedure of adoption was not followed by them.
Recently, the step-parents used to allegedly torture the boy by beating him with stick and also burnt his body parts, he said.
Some neighbours of the step-parents got to know about it and called up the child line foundation whose volunteers today rescued the boy and lodged a complaint against his parents, he said.
The child has been shifted to a rescue home at Machavaram village under Naguluppalapadu mandal of Prakasam district.
