SINGAPORE - Candidates who posted election advertisements on social media on Cooling-off Day have been reminded by the Elections Department (ELD) of the ban in place on electioneering.

In a statement, the ELD noted that there were several election advertising posts on Twitter and Facebook by a few candidates and parties during the early hours of Cooling-off Day.

It cited the People's Action Party, People's Power Party and Reform Party as examples.

"Upon noticing these postings, the Assistant Returning Officer reminded these candidates and parties of the rules which prohibit election advertising on Cooling-off Day," the ELD said.

The posts have since been taken down.

Minister for Environment and Water Resources Vivian Balakrishnan, a PAP candidate in Holland-Bukit Timah GRC, was one of those whose Facebook and Twitter accounts were updated on Cooling-off Day.

In a post just before 2am, he described his day of campaigning in the Cashew ward of Holland-Bukit Timah GRC.

Dr Balakrishnan later said his Cooling-off Day posts were an automatic repeat of a Facebook post he had originally uploaded on Sept 4.

As his Facebook and Twitter accounts were linked, an associated tweet was also generated at the same time, he said.

"We have contacted Facebook to conduct an investigation into the source of this bug. We have also requested that the page be locked down to prevent any further postings."

Facebook later replied in a statement, saying: "A bug in our technical system led to recurrent auto-posting on Dr Vivian Balakrishnan's Facebook page. We are sorry for the inconvenience caused."

On Cooling-off Day, the traditional day of campaign silence before voters cast their vote on Polling Day, candidates cannot campaign and election advertising must not be published.

First introduced in 2011, the day is meant to give voters a chance to reflect rationally on various issues raised during the election period before voting.