The incident took place yesterday when the accused Zahir Abdul Sattar Khan, a resident of Nashik, reached the girl's house in Mumbra here and stabbed her using a sharp weapon, SM Munde, Sr PI of Mumbra police station said.
On hearing the girl's cries for help, her father Arif Khan (40) rushed in for rescue but was attacked by Sattar. The accused is the victim's maternal cousin and had proposed marriage when her family had visited Nashik a week ago, but was refused, police said.
The body of the girl has been sent for postmortem and Khan has been admitted to the civic hospital at Kalwa.
Sattar is absconding since the incident and a manhunt has been launched for him. He has been charged under various sections of the IPC, police said.
According to police, the accused earlier during the day called up the family of the victim over the cell phone to confirm who all were at home before he arrived in Thane.