Eritrea has been named the most censored country in the world by the Committee to Protect Journalists (CPJ).
A report by the New York-based press freedom organisation has analysed press restrictions around the world to coincide with World Press Freedom Day tomorrow. North Korea, Syria and Iran hold second, third and fourth places respectively.
CPJ's executive director Joel Simon said: "In the name of stability or development, these regimes suppress independent reporting, amplify propaganda and use technology to control rather than empower their own citizens.
"Journalists are seen as a threat and often pay a high price for their reporting. But because the internet and trade have made information global, domestic censorship affects people everywhere."
The study was based on 15 benchmarks including the blocking of websites, the absence of independent or privately owned media, restrictions on electronic recording and journalist movements, and other rigid censorship laws.
The last report was published in 2006 and many of the same countries are on the list.
Of Eritrea, the report said that "no foreign reporters are granted access ... and all domestic media are controlled by the government." The media that is allowed to operate must report to the country's information minister. The government expelled the last accredited foreign correspondent in 2007.
An exiled Eritrean journalist told the CPJ: "Every time [a journalist] had to write a story, they arrange for interview subjects and tell you specific angles you have to write on. We usually wrote lots about the president so that he's always in the limelight."
The findings also have worrying implications for the West's relations with North Korea, Syria and Iran, particularly with regards to their nuclear weapons programmes. While North Korea has confirmed tested nuclear weapons, Iran is believed to be developing them and it is alleged that Syria has nuclear ambitions.
A lack of press freedom also represents a crackdown on democracy. According to the CPJ, North Korea, the worst offender in the 2006 study, "remains an extraordinarily secretive place."
It said censorship had "intensified significantly in Syria and Iran in response to political unrest". Foreign journalists are no longer officially granted access into Syria and local reporters are restricted from moving freely around the country.
The CPJ said that Iran has blocked websites and imprisoned journalists to limit publication and broadcast of information.
The other countries on the censorship list, in order of the worst offenders, are Equatorial Guinea, Uzbekistan, Burma, Saudi Arabia, Cuba and Belarus.