|Reporters Without Borders said Bahrain "bolstered its censorship efforts" after the start of the uprising last year.
Reporters Without Borders has updated its 2012 "Enemies of the Internet " list to include Bahrain and Belarus.
The updated list, which was released on Monday to mark what the organisation called "World Day Against Cyber-Censorship", still includes countries such as China, North Korea and Saudi Arabia from the previous year.
The Paris-based non-governmental organisation that advocates freedom of the press said that internet users in 2011 were "at the heart of the political changes in the Arab world and elsewhere".
In Bahrain, RWB said, the government "has bolstered its censorship efforts" in reaction to the pro-democracy uprising that began on February 14, 2011.
"Bahrain offers a perfect example of successful crackdowns, with an information blackout achieved through an impressive arsenal of repressive measures: exclusion of the foreign media, harassment of human rights defenders, arrests of bloggers and netizens (one of whom died behind bars), prosecutions and defamation campaigns against free expression activists, disruption of communications," the report said.
In Belarus, RWB said, "The Internet – a mobilisation and information platform – has received the full brunt of the authorities’ brutal crackdown on the opposition."
The report continued that "some 100 Belarusian journalists were interrogated in 2011 alone, and over 30 given prison terms".
Libya, where the government of Muammar Gaddafi was overthrown in a violent revolt, was removed from the list of "countries under surveillance".
"In Libya, many challenges remain but the overthrow of the Gaddafi regime has ended an era of censorship," the report said.
Venezuela was also removed from that list, whereas India and Kazakhstan were added to it.
"On World Day Against Cyber-Censorship, we pay tribute to the ordinary citizens who often risk their lives or their freedom to keep us informed and to ensure that often brutal crackdowns do not take place without the outside world knowing," RWB said.