A 17-year-old college student has been apprehended for allegedly stalking a girl he befriended on Instagram and pressuring her to send him nude photos with the threat of circulating her already available private pictures on social media, police said on Friday.

It has also been alleged that the accused, who is pursuing his graduation from the School of Open Learning here, accosted her and demanded sexual favours.

Upon checking the accused's phone, it was revealed that he was harassing other girls using the same modus operandi, police claimed. According to them, he had forced his parents to buy him an iPhone which he used to show off to these girls.

The accused was apprehended on January 26.

The matter came to light when the victim's father complained to police on January 25 that his 14-year-old daughter shared her photos and videos with someone through Instagram chats and he feared that those videos might get circulated.  However, he was initially reluctant to initiate legal action and as such both the victim and her father were counselled, police said.

The victim disclosed that she had shared her private pictures and video with a friend on Instagram who was pressurising her to start inappropriate chats and send him more such photos, police said. Based on the girl's statement, a case was registered, they said.

Deputy Commissioner of Police (North) Sagar Singh Kalsi said that during the investigation, it was found that the SIM card to which the IP address of the accused was registered belonged to a 50-year-old man.

The seller of the SIM card said that he has no details available with him except for the Aadhar number which was used to buy the car, the police officer said.

The police then began enquiring with grocery store owners and local vendors by showing the photo of the accused obtained from Instagram. The boy was finally identified and it was revealed that he was using a SIM issued on his father's, he said.

Since the boy was not available at home, his father was directed to present him at the police station. "The accused told police that he came in possession of some private pictures of a girl and started following her on Instagram. He kept her private pictures saved on his mobile phone and used to stalk her online all the time.

"After befriending her, he started asking for her nude photos. But when the girl declined, he showed the nude photos he already had with him and demanded more such photos and sexual favours online," the DCP said.

A case under Indian Penal Code sections 354A (sexual harassment), 354D (sextortion) and relevant sections of the Protection of Children from Sexual Offences (POCSO) Act.