He was three times her age but lied that he was 18 and had unprotected sex with her a day after he got to know her online.

Muhammad Hudri Ahmad, 37, was jailed for a total of 40 months yesterday after admitting to three charges of sex with a minor.

He was a part-time events manager when he added the 13-year-old schoolgirl as a friend on Instagram on May 12 last year.

The Secondary 2 student met him the next day at the fourth-floor staircase landing of an HDB block in Ang Mo Kio Avenue 3.

He began kissing and touching her before having unprotected sex with her, Deputy Public Prosecutor Eunice Lau said last month.

They met again a week later and had sex at the same staircase landing.

The following month, she felt guilty and wanted to break up with him. Hudri then threatened to tell her mother that she was no longer a virgin, so she continued to remain in the relationship.

On June 29, she went to Hudri's flat in Hougang Avenue 8 to meet him, accompanied by a schoolmate.

That evening, Hudri had sex with the girl in his bedroom after her schoolmate left.

Police arrested him the next day.

DPP Lau cited multiple aggravating factors when she sought a 24-month sentence.

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

District Judge Low Wee Ping sentenced Hudri to 20 months per charge with two to run consecutively. Seven other charges were considered during his sentencing.

The maximum penalty is 10 years' jail and a fine per charge.