The victim’s father filed the case with Kotalipara police against Ali Hossain, son of Mahsin Hawladar of Purnaboti village of the upazila, said Sub-Inspector Mohammad Himel.
According to case statement, Hossain and his friend Masum Hawladar forcibly took the ninth-grader to a fish enclosure, owned by one Ibrahim Hawladar, on Saturday morning.
As Ali Hossain raped the girl, Masum recorded the incident on his mobile phone.
They threatened to circulate the video online if she did not keep silent.
Mohammad Zakaria, inspector of Kotalipara Police Station and also the investigation officer of the case, said the victim will be sent to a local hospital for medical test on Tuesday.
No arrest has been made yet.
Media reports compiled by Ain O Salish Kendra show that 632 rape incidents took place between April and August this year.