Fifteen Singaporean "protesters", between 16 and 27 years old, "are currently assisting" in investigations into possible offences of organising and/or taking part in a public assembly without permit, police said.
In a statement Tuesday evening, police said that a group of 12 men had gathered at the vicinity of City Hall MRT station on 5 November this year dressed in red or black. Three of them wore Guy Fawkes masks and a total fo 14 masks were found in their possession.
Also on the same day, at about 10:15pm, two other men and a woman were seen with masks along Orchard Road.
"These 15 subjects had responded to online postings calling for 24-hour protests globally in support of a movement called the “Million Mask March” to commemorate Guy Fawkes Day on 5 November 2013," police said.
This was "despite a Police advisory reminding the public that organising or participating in a public assembly without a Police permit is illegal and may constitute an offence under the Public Order Act," they added.
The police issued the advisory earlier this month after a hacker called "The Messiah" and claiming to be part of the Anonymous internet network left a message on 1 November on a blog site of The Straits Times saying that on 5 November, "we shall paint the streets red and black with our attires and when you see your fellow comrades in black and red, smile and shake their hand."
The message also said, "Let us use that day to demonstrate our new undivided unity even in the amidst of all our differences. This is a very important stage in regaining your freedom."
The police's statement about the 15 Singaporeans "assisting" police investigations comes after a 35-year-old Singaporean, James Raj Arokiasamy, was charged in court Tuesday morning under the Computer Misuse and Cybersecurity Act over the defacing of the Ang Mo Kio Town Council website on 28 October this year.