Media freedom suffered a "drastic decline" worldwide last year in part because of extremist groups such as Islamic State (IS) and Boko Haram, the watchdog group Reporters Without Borders said in its annual evaluation released Thursday.

"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 was an 8 percent increase in violations of freedom of information in 180 countries and regions in 2014 compared to the 2013, according to its statistically weighted calculation.

All parties in conflicts raging in the Middle East and Ukraine were waging "a fearsome information war" where media personnel were directly targeted to be killed, captured or pressured to relay propaganda, it said.

IS group active in Syria and Iraq, Boko Haram in Nigeria and Cameroon, and criminal organizations 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.

The best-rated nations were northern European states such as Finland, and Sweden, with New Zealand, Canada and Jamaica also making the top 10.

But some other European countries did not do so well. Italy, for instance, fell 24 spots to 73rd position because of mafia threats and "unjustified defamation suits." Overall, "the EU appears to be swamped by a certain desire on the part of some members states to compromise on freedom of information," the report said.

The US 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.