SINGAPORE - A 70-year-old man who was shown in a now-viral video shouting at and slapping a foreigner on a train has been arrested for causing public nuisance and voluntarily causing hurt.

The police on Saturday (April 22) said they received a report on Friday (April 21) about a man repeatedly using offensive language and assaulting a commuter on an MRT train.

The victim, Joe DeMarini, uploaded the video on his Facebook page on Thursday (April 20). The incident reportedly happened on the North East Line on Wednesday (April 18) night.

He said the man was allegedly drunk and approached him and a friend and made sexual advances on him.

When Mr DeMarini's female friend intervened, the man allegedly yelled and threatened her.

Others on the train stepped in too, while several were taking videos, he said.

"He touched me, and I told him not to, and I briefly lost my temper - after that he slapped me on the side of the head," Mr DeMarini alleged.

The 4min 22sec clip has been viewed more than 1.2 million times.

Mr DeMarini, who is from Pennsylvania, received an outpouring of support from Singaporeans afterwards, with many apologising on the man's behalf and welcoming him to Singapore.

Officers from Ang Mo Kio Division identified the suspect and arrested him along Ang Mo Kio Avenue 1 on Friday at about 10pm.

Those convicted of the offence of public nuisance can be fined up to $1,000, while those convicted of the offence of voluntarily causing hurt can be jailed for up to two years and or fined up to $5,000.