City police chief Fadil Marsus said the incident occurred on Thursday around 7.20pm, when an unknown man allegedly touched the victim’s buttocks in a train coach.

“With the train being crowded at the time, the complainant could not clearly see the suspect’s face as he was wearing a mask,” Fadil said in a statement.

The case is being investigated under Section 354 of the Penal Code for committing assault or use of criminal force to a person with the intent to outrage modesty.