SINGAPORE - A 20-year-old former gang member told the High Court on Wednesday (Jan 17) that he felt helpless at being unable to stop his leader from repeatedly raping a 13-year-old girl who was his friend.

Fu Yiming, who was 16 at the time of the alleged rapes, said he would like to apologise to the girl for doing "a poor job" as her friend. She is now 17.

On one occasion, he tried to protect her by claiming to be her boyfriend, but was punched and kicked to the ground by his leader. On another occasion after that, he walked away on the pretext of getting a drink.

Fu was testifying on the second day of the trial of 25-year-old Koh Rong Guang, also known as Charles, who is charged with raping the girl on four occasions between November 2013 and January 2014. Koh also faces charges for other offences, including criminal intimidation and causing hurt.

The alleged rapes took place at the staircase of a karaoke outlet in Choa Chu Kang Centre and a block of flats in Choa Chu Kang Crescent.

The girl made a police report in July 2014 after photographs that Koh had taken of her and Fu in a sexually explicit position trended on social media platforms.

Fu, who is currently serving a sentence at a reformative training centre for money laundering, told the court that although he knew about the rapes, he did not dare make a police report as he was afraid of Koh, who headed their gang of seven.

He said the group's main activity was to "get into fights regularly" and he was the main person who executed Koh's orders.

The gang usually hung out at Lot One shopping mall in Choa Chu Kang, and it was there that Fu met the girl in October 2013.

About a month later, Koh told Fu that the alleged victim had badmouthed Fu's girlfriend.

"I told Charles to settle it for me. I did not want my girlfriend to misunderstand the relationship between me and (the girl)," Fu told the court.

Fu said Koh later told him that he had scolded the girl.

A few days later, the group spotted the girl at Lot One. Koh took her to the staircase at a karaoke outlet at the adjacent Choa Chu Kang Centre, telling the other members to wait with his girlfriend.

Koh later told his gang that he had sex with the girl and sent them a nude photo of her.

Fu said he later found out from the girl that Koh had raped her twice.

In the third incident, Koh took Fu and the girl to a staircase at a block of flats. Fu said he tried to intervene by claiming to be her boyfriend but was assaulted by Koh instead.

He said Koh was about to hit him with a brick when the girl pleaded with him to stop and agreed to have sex with him.

Afterwards, Koh made Fu and the girl pose in a compromising position and took photos of them, so that she would not go to the police. Fu said Koh also egged him on to have sex with the girl, but he declined.

"I apologised to (the girl) for not being able to protect her," he said.

On the fourth occasion, Koh was with Fu and two others when he took the girl to a staircase. Fu left to get a drink. When he returned, Koh was done and asked the two others to have sex with her but they said no.

The trial continues.