Neetu alias Gudiya was kidnapped by her uncle Rakesh Kumar yesterday while she was asleep and killed after taking her outside the village, they said.
Later he dissected the body and took out the heart and kidney, they said.
When the victim's father, Chandrika Prasad, reached the spot searching for his daughter, he found that Rakesh was preparing to perform exorcism with the body and the organs, it said.
The accused has been arrested along with his lover Phulau as she is suspected to be his accomplice, they said.
Rakesh confessed of killing his niece and investigation in the case is underway, police added.