On 18 April, the girl, hailing from Bombe Pada hamlet of Mohili village in Thane, had gone to attend the wedding in nearby Sontakke village.
After the function, she was sleeping in a room at the marriage venue. The accused, identified as Mayur Mukne (19) who works at a brick kiln, forcefully took the girl out of the room to an isolated location where he allegedly raped her, Sub-Inspector Sheetal Bamne said.
Two other acquaintances of the accused, Harish Bombe and Uday Bombe, both brothers, who had also gone to attend the marriage, later allegedly threatened the victim with dire consequences if she revealed the incident to anyone, she said.
Out of fear, the girl did not inform the police immediately after the incident, but later mustered courage and lodged a complaint on Monday morning.
The victim and the three accused are residents of the same Bombe Pada hamlet in Mohili village.
Offences have been registered against the three accused under sections 376 (rape), 323 (voluntarily causing hurt), 504 (intentional insult with intent to provoke breach of the peace) and 506 (criminal intimidation) of the IPC and also sections 4 and 21A of the Protection of Children from Sexual Offences (POCSO) Act, police said.
A manhunt has been launched to nab the three accused, police added.