The media rights group Reporters Without Borders has expressed concern about Internet censorship and other threats around the world to free expression online.
In a report released Thursday, called "Enemies of the Internet", the group listed 12 nations that it said have systematically restricted their populations from accessing online news and information deemed "undesirable."
The nations cited were China, Burma, North Korea, Vietnam, Egypt, Iran, Syria, Saudi Arabia, Turkmenistan, Uzbekistan, Cuba and Tunisia.
The report alleged these countries not only restrict access to Web sites, but also persecute some computer users for what they post online.
The U.S. State Department has also expressed concern about Internet freedom and in recent years began assessing Internet censorship and harassment of online dissidents.
Last year, China was criticized for promising reporters full Internet access as they covered the Beijing Olympic Games, but then blocking access to some sites. China said later that journalists would have full access to sites not deemed illegal by Chinese authorities.
China has also said some Web sites violate the country's anti-separatist law by promoting a "Two Chinas" policy that calls for an independent Taiwan.