SINGAPORE — Over a period of three months, a man allegedly raped a schoolgirl almost half his age four times before getting someone to circulate compromising photos of her and a mutual friend on Facebook.

Koh Rong Guang, who was 21 when he allegedly committed the offences against the 13-year-old victim, took the stand on the opening day of his eight-day trial on Tuesday (Jan 16) after he denied all charges.

Now 25, he was charged with four counts of rape, one count of sexual assault by penetration for getting the victim to perform oral sex on him, two counts of procuring or committing an indecent act with a young person, one count of circulating an obscene image, three counts of criminal intimidation, and one count of voluntarily causing hurt.

On Tuesday, Deputy Public Prosecutors David Khoo and Sruthi Boppana said in court that 15 witnesses will be called to prove the case against Koh, who was reportedly the leader of a teenage gang.

The witnesses include the victim, who cannot be named due to a gag order, as well as four other boys from Koh’s gang.

The court heard that the victim got to know Koh in late 2013 through a male friend Fu Yiming, then 16, who was a member of Koh’s gang. She alleged that Koh sexually assaulted her on “numerous occasions” — four instances of which she has the most vivid recollection.

The alleged assaults took place at two staircases — one near the K-Box entertainment outlet in Choa Chu Kang Centre, and another at Block 672A, Choa Chu Kang Crescent.

The first time she was allegedly raped, the victim recalled that Koh had isolated her at the K-Box staircase while confronting her about a dispute she apparently had with Fu’s then girlfriend.

A few weeks later, Koh allegedly cornered her again at the same staircase, threatened her with a spanner, and then forced her to perform oral sex on him before raping her.

He allegedly took a nude photograph of the victim, before sending the image to Fu on Jan 19, 2014.

Koh allegedly raped the victim again some time between December 2013 and Jan 24, 2014. That day, accompanied by Fu and two other members of his gang, Koh took her to the staircase at Block 672A.

After raping the victim, Koh was said to have asked the two other boys to have sex with her, but they refused. Koh then threatened the three boys not to disclose what they had witnessed.

The fourth alleged rape happened on Jan 25, 2014, when Koh asked the victim to meet him at the same staircase.

Fearful of what Koh would do to her, the victim got Fu to accompany her. When they met, Koh allegedly punched the boy’s face and kicked his body, then threatened the victim and the boy with a brick.

In her bid to stop Koh from harming them, the victim gave in to the assailant and followed him to a different floor where he raped her.

Thereafter, Koh purportedly directed Fu to strip and pose with the victim, who was exposed, so that he could take sexually compromising photographs of them.

Koh allegedly made a collage out of three of those photographs that day, and sent it to another person, asking that it be posted on Facebook.

If convicted of rape and sexual assault by penetration of a minor, Koh could face a jail term of between eight and 20 years, and up to 12 strokes of cane.

For procuring or committing an indecent act with a young person, Koh could get up to five more years in jail, or a fine of up to S$10,000.