The accused, Kattu Raja, has been arrested, they said.
The 15-year-old girl committed suicide by setting herself ablaze when she was alone at her home in Duraisamypuram last night, police said.
Her mother was away at work during the time of the incident. Neighbours, who heard the screams rushed her to a nearby hospital where she died during the treatment, police said.
She told the neighbours that she had taken the extreme step as she was unable to put up with the continuous sexual harassment of Kattu Raja.