"There has been an overall deterioration linked to very different factors, with information wars, and action by non-state groups acting like news despots," the head of the Paris-based group, Christophe Deloire, told AFP.
The Reporters Without Borders 2015 World Press Freedom Index stated that there were 3,719 violations of freedom of information in 180 countries in 2014 - eight per cent more than a year earlier.
The Islamic State group active in Syria and Iraq, Boko Haram in northern Nigeria and Cameroon, and criminal organisations in Italy and Latin America all used "fear and reprisals to silence journalists and bloggers who dare to investigate or refuse to act as their mouthpieces," said the watchdog, known by its French initials RSF.
North Africa and the Middle East contained notable "black holes" in which "entire regions are controlled by non-state groups in which independent information simply does not exist," the group said.
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RSF's ranking put Iran, China, Syria and North Korea among the countries with the very worst levels of press freedom out of the 180 evaluated.
India is ranked 136th in the world, the report said.
Repression of journalists in Ukraine during its early-2014 uprising against its pro-Kremlin president, and in Turkey during anti-government demonstrations earned both spots in the bottom quarter of the table.
The best-rated nations were northern European states such as Finland, Norway, Denmark, the Netherlands and Sweden, with New Zealand, Canada and Jamaica also making the top 10.
The United States ranked 49, three spots lower than in the previous report, in part because of what RSF said was the US government's "war on information" against WikiLeaks and others.