A man on Monday wielded a samurai sword on board an MRT train, half-dressed in the attire of a Japanese martial art exponent.
He jumped the fare gate, boarded the train at Paya Lebar station, and alighted at City Hall, said the police in a statement on Monday.
He was eventually arrested at 1.16pm in Victoria Street near Bugis station, after a chase by police officers.
Police got a call for help at 12.46pm from MRT staff at Paya Lebar station.
When officers boarded the train travelling towards City Hall, "a man was found in possession of a sword", the statement said.
The officers kept the man away from other commuters "so as not to aggravate the situation while they continued to monitor the subject and followed him closely when he alighted at City Hall MRT station", it added.
The police are continuing their investigations. Eyewitnesses said the man, with frizzy shoulder-length hair and wearing a Hard Rock Cafe T-shirt, was mumbling to himself.
Media manager Kwok Kar Wai, 36, saw him outside Raffles City Shopping Centre waiting at the traffic light to cross the road towards Raffles Hotel. He seemed to be "taking a walk at a very relaxed pace", despite being tailed by "four or five" policemen, she said.