A bus driver who spotted a passenger with his mask down stopped the bus to approach the man and advise him to put on his mask properly. The passenger then followed the driver back to the driver's seat and hurled vulgarities at him.

Mohamed Reezal Abdullah, 49, was yesterday fined $3,500 under the Protection from Harassment Act for using abusive language against a public service worker. Another charge of failing to cover his nose with his mask was taken into consideration in his sentencing.

The court heard that at about 7.30pm on July 20 last year, Mohamed Reezal, a Singaporean, boarded SBS service 10 and took a seat in the upper deck of the bus.

The bus driver, Mr Chua Khea Boon, 61, saw on the closed-circuit television that Mohamed Reezal's mask was not covering his nose and mouth. He stopped the bus and went to the upper deck to advise the passenger to wear his mask properly. He then returned to the driver's seat to resume the journey.

But Mohamed Reezal came down to the lower deck as well and confronted Mr Chua at the driver's seat in an aggressive manner.

The victim, fearing for his safety, called SBS' site office to report the matter, said Deputy Public Prosecutor Cheah Wenjie.

For about five minutes after that, as Mr Chua was driving the bus in Marine Parade, Mohamed Reezal used abusive words on the driver.

Mohamed Reezal was represented by Regent Law's Mr Kalaithasan Karuppaya, who told the court that his client was apologetic and understands the seriousness of the offences.

For using abusive words on a public service worker while the worker is executing his duty, Mohamed Reezal could have been fined up to $5,000, jailed for up to 12 months, or both.