Facebook said Monday Singapore's use of an online misinformation law is "severe" and risks stifling free speech, after the company was again forced to block a page in the city-state.

It was the latest criticism from the tech giant over legislation that empowers ministers to tell internet platforms to put warnings next to posts they deem false and order the blocking of pages.  Fringe political website the National Times Singapore was accused of making false statements via its Facebook page, including a claim that "every criticism" of the government had been outlawed under the disinformation law.

The site was ordered to erect a banner flagging it was false -- but it refused, and Facebook was ordered to block access to the site's page in Singapore. Asked about the government request to block the page, Facebook said the company was "legally compelled" to comply.

But a spokesperson added that "blocking orders like this are severe and risk being misused to stifle voices and perspectives on the internet". "Freedom of expression is a fundamental human right, and we work hard to protect and defend this important civil liberty around the world."

The page was run by anti-government activist Alex Tan, who lives in Australia and has been repeatedly accused of spreading falsehoods on a variety of subjects. Four Facebook pages that he operates have now been blocked, according to authorities.

A Singapore government website aimed at debunking untrue information claims that Tan "continues to publish falsehoods that distort the public's understanding of the (misinformation) law and how it has been implemented".

Other tech giants, including Google and Twitter, as well as rights groups have expressed concerns about the law, which came into force in October. The government's political opponents have also raised concerns that it is being used to suppress criticism ahead of elections expected within months.

But authorities insist the measure is necessary to stop falsehoods from circulating online that could sow divisions in the multi-ethnic, multi-faith country of 5.7 million.