Police arrested Israfil,14, his brother Sayed,20, Imam Uddin and Adita's former coaching teacher Abdur Rahim Roni,20, on Thursday night from different areas in Noakhali as suspects, said Md Shahidul Islam, superintendent of Noakhali district police during a briefing on Friday.
Law enforcers also seized a knife from the spot allegedly used in the murder, he said.
Adita left Roni's coaching centre a few days ago to start private lessons elsewhere which might have angered him, police suspect.
On Thursday afternoon, Roni along with the other accused entered the girl's house and violated her. She was alone there at that time as her mother went out of home, added the SP.
Returning home, Adita’s mother found her daughter in a pool of blood with her throat slit and informed police.
Later, police recovered the body around 9:00pm and sent it to hospital for an autopsy, said the police official. Legal steps are under process in this regard, he added.