The girl's relatives informed the Delhi Commission for Women (DCW) helpline, following which the three accused were arrested, they added.
The fourth accused hasn't been arrested yet since he has gone to Bihar for his wedding, the panel said in a statement.
The victim had befriended a man working in a factory around a year back.
After a few days in the relationship, he got intimate with the girl on the pretext of marriage. Later, his three friends allegedly raped the girl on separate occasions in the last one year, police said.
But on May 31, she narrated her ordeal to her mother, who informed some of her relatives. The relatives called the DCW helpline yesterday following which, the three accused were arrested.