Facebook published a correction on a user's post on Saturday November 30th following a demand from Singapore, the first time a tech giant has complied with the city-state's law against misinformation.
The amendment follows "scurrilous accusations" of election rigging, AFP reported.
The law provides ministers with the power to tell media platforms to put warnings next to posts they deem false, but activists fear it could be used to curb free speech.
A post by Alex Tan, who runs the anti-government website the States Times Review, had a correction notice placed below it after a government request, Facebook confirmed. Tan had refused to alter the content, saying he is an Australian citizen and would not comply with requests from a "foreign government".
The controversial item now appears with a label below it, stating that "Facebook is legally required to tell you that the Singapore government says this post has false information".
It also contains a link to the government's fact-checking website, according to Arab News.
"As required by Singapore law, Facebook applied a label to these posts, which were determined by the Singapore Government to contain false information," said a Facebook spokesperson.
The usage of the law comes as speculation mounts that elections could be called within months, although a weak opposition is seen as no match for the long-ruling People's Action Party.
Singapore used the law for the first time Monday, ordering opposition party member Brad Bowyer to correct a Facebook post authorities said could "smear the reputation" of two state investment funds.
Facebook, a large investor in Singapore, has plans to build a $1 billion data centre there and has its Asia headquarters in the city-state.