Facebook said on Saturday it had issued a correction notice on a user's post at the request of the Singapore government, but called for a measured approach to the implementation of a new "fake news" law in the city-state.

"Facebook is legally required to tell you that the Singapore government says this post has false information," said the notice, which is visible only to Singapore users.

The correction label was embedded at the bottom of the original post without any alterations to the text.

The post, which contained accusations about the arrest of a supposed whistleblower and election rigging, was published by Alex Tan, who runs the States Times Review blog. Singapore, which is expected to call a general elections within months, said the allegations were false and scurrilous and initially ordered Tan to issue the correction notice on the post.

Tan, who does not live in Singapore and says he is an Australian citizen, refused and authorities said he is now under investigation.

After authorities ordered Facebook to put a correction next to the post, the social media giant said it had complied.

"As required by Singapore law, Facebook applied a label to these posts, which were determined by the Singapore government to contain false information," a spokesman for Facebook said in an emailed statement.

"As it is early days of the law coming into effect, we hope the Singapore government's assurances that it will not impact free expression will lead to a measured and transparent approach to implementation," the statement goes.

(With input from Reuters and AFP)