RSF claims that the Google-owned blog hosting service has been blocked since 3 October. Users can read blogs hosted under the blogger domain but can't log in to update their own blogs.
The Saudi Internet Services Unit (ISU) told RSF that it had blocked access to blogger.com but would not give any reason. The ISU is responsible for enforcing web filtering and censorship but instructions on blocking content are given by the security services.
More than 400,000 political, religious and sexually-orientated sites are blacklisted in the kingdom.
"Saudi Arabia is one of the countries that censors the internet the most, but blog services had not until now been affected by the ISU's filters," said a spokesperson for RSF.
"The complete blocking of blogger.com, which is one of the biggest blog tools on the market, is extremely worrying. Only China had so far used such an extreme measure to censor the internet."
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