A 40-year-old man was arrested on Monday for committing an obscene act on a public bus, as his plucky teenage victim sounded the alarm.

The alleged act occurred on board SMRT bus service 106 heading towards Bukit Batok bus interchange during the evening peak hour at about 6pm, the police said in a statement on Wednesday. The 17-year-old victim, although "shocked by the brazenness of the act", retained her composure and sought the assistance of the bus captain to detain the subject and call the police, the statement added.

Investigations are ongoing. If charged and found guilty, the man could face a jail term of up to three months and/or a fine.

Deputy Assistant Commissioner of Police Wilson Lim, the commander of Jurong Police Division, praised the victim for reporting the case "despite the shock of confronting the subject in his lewd act".

He added that the police will take firm action against such perpetrators of obscene acts to ensure the safety of commuters on the local public transport network.