Police in separate drives on Monday night detained four people from different areas of Chapainawabganj town in connection with the cases for raping a madrasa student and a college girl yesterday and on September 6.
The arrestees are Jahangir Alam, 32, Jibon, 21, Parvez Islam Ramim, 21, and Nayem Azad, 29.
The incidents came to light when three separate cases were filed, two for rape and another under Pornography Act, with Sadar Model Police Station.
According to the case statement, Jahangir, a distant relative of the 14-year-old madrasa girl, intercepted her while she was returning home from the madrasa in Dariapur area in the town on Monday afternoon.
He then forcibly took the teenager to a nearby isolated place and raped her there.
The victim is now undergoing treatment at Chapainawabganj Sadar Hospital, police said.
In another incident, the three other arrestees -- Jibon, Rahim and Azad -- along with their six other accomplices entered the house of a college girl in Maharajpur area when none of her family members were present on September 6.
The nine then gang-raped the girl and filmed the incident on their mobile phones.
They later spread the video footage of the rape in the locality from their cell phones.
On Monday night, the victim filed two separate cases, one for gang-rape and another under Pornography Act, accusing nine people, including the three arrestees.