A man who runs a pro-People's Action Party Facebook page and three others behind a socio-political website have received stern warnings from the police for online posts they made during last year's Bukit Batok by-election.

Mr Chua Chin Seng, who runs the Fabrications About The PAP Facebook page, as well as Mr Kumaran Pillai, Mr Ravi Philemon and Mr Alfred Dodwell, who are involved in The Independent Singapore website, had published online articles on Cooling-Off Day and Polling Day of the by-election, which were on May 6 and May 7 respectively.

By doing so, they had breached the prohibition of election advertising on those days and committed an offence under the Parliamentary Elections Act, a police statement said yesterday. "Upon careful consideration of all the circumstances of the cases, including the nature of the publications, the Attorney-General's Chambers decided to administer stern warnings to all parties. Should any of the parties commit similar offences in subsequent elections, the stern warning that was administered can be taken into consideration in the decision to prosecute," the police said.

The police had begun investigating both outfits last year after receiving police reports following the May by-election.

An officer from the Elections Department (ELD) had filed a police report against The Independent Singapore for publishing articles on Cooling-Off Day and Polling Day. The website had continued to post articles in violation of the rule, even after receiving a specific reminder from the by-election's Assistant Returning Officer not to do so, the ELD had said. Three weeks later, Mr Augustine Lee of opposition People's Power Party made a police report against Fabrications About The PAP. He said the page had put up two Facebook posts on Polling Day.

Election advertising, which includes posts intended to enhance the standing of a party or candidate or to promote their electoral success, is prohibited on Cooling-Off Day and Polling Day. Under the Parliamentary Elections Act, a person who posts election advertising on those days may be fined up to $1,000, jailed for up to 12 months, or both. Cooling-Off Day is meant to allow voters time to reflect rationally on issues raised before they vote.

Yesterday, the police reiterated this, saying: "The Cooling-Off Day breaches detected during the 2016 Bukit Batok by-election go against the spirit of the election rule. Left unchecked, such breaches can undermine public trust in Singapore's electoral process."