SINGAPORE - A part-time events helper had sex with a 13-year-old girl a day after meeting her online and coaxing her to be his girlfriend.

Although Muhammad Hudri Ahmad was three times her age, he lied that he was 18 during their chat on Instagram on May 12 last year.

On their first meeting, he took the victim, who was in her school physical education uniform, to a staircase landing in Ang Mo Kio Avenue 3 and had sex with her.

She experienced pain and tried to push him away but he told her to "get used to it'' and continued to penetrate her against her wishes, said Deputy Public Prosecutor Eunice Lau.

A week later, he had unprotected sex with her at the same staircase landing.

In June 2015, the girl had asked to break up with him as she felt guilty about the sexual relationship but Hudri became angry and threatened to tell her mother about their relationship. The girl backed off.

On June 29, she went to his home and Hudri had sex with her. She stopped him when he tried to have unnatural sex with her. She spent the night at his home and he was arrested the next day when police came knocking at his door.

Skype conversations extracted from his laptop showed that he had engaged in "dirty talk'' on multiple occasions with the victim and exploited her naivete.

In her victim impact statement, the girl stated that besides feeling disgusted with herself and emotionally unstable, she had also taken to cutting herself as she felt she deserved such pain. She is now seeing a private psychiatrist and undergoing regular counselling and is on medication to keep her emotions in check.

Arguing for a 24-month jail sentence on each of three charges, DPP Lau said: "The accused is a grown man of 36 years old. His actions cannot be dismissed as mere momentary folly, in particular, when viewed in context of his multiple counts of intercourse and prolonged sexual conversations with the victim, even after she expressed her discomfort.''

She said the sentence meted out should adequately deter like-minded offenders from preying on vulnerable victims, while addressing the public disquiet in relation to adults who exploit minors like the victim to satisfy their own selfish lust.

Hudri, represented by Criminal Legal Aid Scheme-assigned lawyer Raeza Khaled Salim Ibrahim, was sentenced to 40 months' jail on Thursday (Sept 1) after he admitted to three charges of sexual penetration. Seven other charges were taken into consideration.

District Judge Low Wee Ping backdated his sentence to Oct 9 last year.

Hudri could have been jailed for up to 10 years and fined per charge.