The police arrested a 22-year-old man on Thursday afternoon in a case of aggravated outrage of modesty along West Coast Road.
The victim, a 25-year-old woman, was attacked on Monday, along the Ayer Rajah Expressway near to West Coast Way, while she was walking back to her home, a condominium apartment.
The suspect, who is unemployed, was cycling on a stolen bicycle along the same path when he attacked her.
He reportedly got off the bicycle and punched her. When she fell, he pinned her to the ground and started to grope her. He ran off as two passers-by approached, leaving behind the bicycle.
The man was arrested at Merpati Road in MacPherson - an area he is believed to frequent - at 2.45pm on Thursday.
Deputy Assistant Commissioner of Police Melvin Yong, the commander of Clementi Police Division, said 60 officers from the division and the Criminal Investigation Department were deployed to interview witnesses and residents in the area, review closed-circuit television footage, and retrieve physical evidence.
Superintendent Chua Teck Wah, head of investigation at Clementi Police Division, said apart from the case involving the 25-year-old woman, there was another case of outrage of modesty reported on Monday in the West Coast area.
Investigations are ongoing to establish if the suspect was involved in the other case. He is currently under police custody.