A 20-year-old man has pleaded guilty yesterday (Feb 19) to using Instagram and Facebook to befriend girls aged 12 and 13 before carrying out a string of sexual offences against them.

Goh Kar Aip even threatened to reveal details of one sexual relationship to the girl's school before a teacher found out what he was doing and a police report was made, reports The Straits Times.

Goh, who is a permanent resident, had turned to social media to look for young girls while waiting for his enlistment in September 2014.

The high court heard that he felt they were "easier to talk to" and would not look down on him for his lack of education.

He would private message his targets and introduce himself as "Kai".

While some ignored him, others responded and chatted with him.

After getting to know them, Goh proceeded to talk about sexual topics and ask them for photos of their stomachs.

After gaining their confidence, he would ask them for their nude photos and sometimes send them photos of his genitalia, hoping they would reciprocate.

In one case, he asked a 12-year-old girl who had just completed her Primary School Leaving Examination (PSLE) to be his girlfriend on their first chat on Instagram.

She agreed because Goh said he liked her.

He took her to his Hougang flat on Dec 19, 2015, where he groped her and made her commit an indecent act on him.

After this encounter, she wanted to break up with him as she was not comfortable being with someone much older than her.

However, she agreed to meet him again and was terrified when he threatened to reveal their text conversation about kissing, hugging and masturbation to her school.

In the same month, he began chatting with another 12-year-old, who had sent revealing shots of herself to him.

They first met at a staircase landing in Tampines on Jan 11, 2016, when he fondled her under her uniform and asked her to perform oral sex on him.

They met another three times over the next three months, during which Goh committed sexual offences against her.

When a teacher heard that a young man was harassing her students she investigated and found out that one of the girls, who was in a relationship with Goh, had taken three of her schoolmates to meet him.

He committed sexual offences against the girl and two of the three friends.

A police report was made on Mar 19, 2016.

A psychiatric assessment on Goh by the Institute of Mental Health found that he did not fulfil the criteria to be diagnosed as a paedophile. However, a psychiatric report said his use of both physical and psychological coercion on the victims likely reflected "an underlying attitude that support or condone sexual violence and would increase his risk of recidivism".

The punishment for the most serious offences, sexual penetration of a minor and sexual assault by penetration, carries a maximum of 20 years' jail and caning .

Read the full story at The Straits Times.