SINGAPORE: Facebook and other sites Friday blocked access to a rap video about race in multi-ethnic Singapore that is under police investigation after authorities asked for the footage to be removed.

The video features an ethnic Indian comedian and YouTube star railing against an advert in which the skin of an actor of Chinese origin is darkened to make him look Indian.

The ad sparked fierce criticism this week in the city-state, where race is highly sensitive -- the country has an ethnic Chinese majority and is also home to Muslim and ethnic Indian minorities, as well as many foreigners.

In her video, comedian Preeti Nair delivers an expletive-filled rap alongside her brother Subhas that appears to target the city-state's Chinese inhabitants, while standing in front of the advert.

Police in tightly-controlled Singapore, which has strict laws against sowing divisions between races, have launched an investigation into the video.

After a request from regulators, some posts of the video could not be accessed on Facebook in Singapore, and a message appeared that said local laws prohibited the site from showing it.

The video was blocked on YouTube alongside a message that it was not available due to a complaint from the government. Twitter also blocked posts related to the footage.

In a statement, Facebook said there were "times when we may have to restrict access to content because it violates a law in a particular country, even though it doesn't violate our community standards".

Twitter declined to comment. YouTube did not immediately respond to requests to comment.

- 'Knee-jerk reaction' -

Media regulator IMDA said that as the video had been shared on social media, it had "issued notices to the individuals and internet platforms for their cooperation to remove the videos."

Several people posted on social media that they had received a letter from the regulator requesting them to take down the video as it was "prohibited" under internet guidelines.

The push to censor the video comes with social media companies already nervous about new legislation in Singapore -- not yet in force -- to combat "fake news" that could see warnings placed next to posts that authorities deem false.

Nair, known by her nickname "Preetipls", and her brother issued an apology Friday for "any hurt that was unintentionally caused" by the video.

But commentators said it was a tongue-in-cheek statement similar to an apology issued by state-owned broadcaster Mediacorp and the creative agency behind the advert earlier this week.

The ad for electronic payments featured Mediacorp actor Dennis Chew playing four different characters -- an Indian man, a Muslim woman wearing a headscarf, and a Chinese man and woman.

The backlash was fierce in the country of 5.6 million, where there have long been complaints the ethnic Chinese majority enjoy greater privileges, despite government efforts to foster racial harmony.

The government has reacted furiously to the rap video, with Law and Home Affairs Minister K. Shanmugam lambasting it as an attack on another race.

But critics said the move to block the rap was another example of the city-state restricting free speech, and Human Rights Watch condemned authorities' "knee-jerk reaction to criminalise the video".

"Singapore's censorship regimen is never far from the surface," Phil Robertson, the group's deputy Asia director, told AFP. —AFP