A gang of men on Monday night pounced on a couple, tied the male companion to a tree and took turns to rape the woman for two hours near the temple town of Srimushnam in Cuddalore district, some 100 km from Chennai.
Ten persons have been identified in connection with the case, the complaint for which was filed by the victim on Tuesday.
Six persons have been arrested and the police are looking for the other four accused, based on the description given by the woman and her companion.
The arrested six have been remanded in police custody.
According to her complaint, they were at a secluded spot on the banks of a river, when three persons accosted them.
The male companion managed to free himself and fled the spot.
The girl was dumped by the attackers after she fell unconscious, the police said. She gave her statement to Cuddalore superintendent of police A Radhika.
Tamil Nadu chief minister J Jayalalithaa on Wednesday said stringent action would be taken against the culprits.
"It is a shocking crime and there is no doubt that deterrent laws should be put in
place and the period of investigation should be shortened so that justice is meted out swiftly. Only that will act as a deterrent in future."