Their visit passes have been cancelled and they were repatriated to South Korea on June 9, it said.
Police investigations established that the other two South Korean men, aged 29 and 31, had not committed any criminal offence.
Security has been upped for the summit, with parts of the city-state in virtual lockdown.
The police department said it would like to remind all foreigners visiting Singapore to abide by local laws and warned that the violators would be dealt with firmly. They said offenders in such cases would likely see their visas or visit passes cancelled, and face repatriation.
Members of the media who commit any offence in Singapore will also not be accredited and denied permission to cover the historic summit between the US and North Korea.
Some 2,500 journalists are in Singapore to report on the historic summit.
(This story has not been edited by Business Standard staff and is auto-generated from a syndicated feed.)