Critics say 'dictatorial' move on island that houses asylum seekers aims to stifle dissent.

The tiny Pacific country of Nauru has blocked access to Facebook in a move criticised as a "dictatorial" attempt to stifle dissent.

As officials insisted the censorship was intended to curb pornography and protect Nauru's "Christian heritage and culture", critics said the remote island nation was seeking to prevent political opposition.

"The first reason they gave [for the closure] was due to a technical problem - now it's all about porn," opposition MP Matthew Batsiua told Australia's ABC News.

"This is all about [government minister David] Adeang and his cronies being worried about the ever-increasing number of people who have taken to social media to criticise his dictatorial style, which even the President is either unwilling - or too scared - to rein in."

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The ban follows a decision last year to introduce an $8000 application fee for journalists who want to visit - a move widely seen as an effort to prevent reporting on Nauru's controversial Canberra-funded detention centre, which holds asylum seekers transferred from Australia.

The nation of about 9500 people is more than 90 per cent Christian and has one of the world's highest unemployment rates. Its ailing economy benefits significantly from the running of the detention centre.

Refugee advocates said the Facebook ban was distressing and would prevent asylum seekers in Nauru from communicating with family members.

"There is quite a deal of dismay and anxiety at Facebook being cut off," Ian Rintoul, from the Refugee Action Coalition, told Fairfax Media.

"For many of them it is a lifeline to their family, to their community, to the outside world ...

"The Australian Government has been only too willing to collaborate with the Nauru Government with the increasingly dictatorial measures it has taken."

Mr Adeang, the Justice Minister, said the internet crackdown was an attempt to protect the country's Christian heritage, claiming "many outside of Nauru do not understand Pacific or Nauruan culture".

"Pornography is not consistent with our faith or our values. As a nation, we have the right and the ability to promote the values that helped build our country, and these include values that are based on scripture."