MEXICO CITY: Three successive Mexican presidents have failed to halt a cycle of violence against journalists and impunity for their killers that is stifling freedom of expression, a watchdog group said on Tuesday. The Committee to Protect Journalists (CPJ) urged President Enrique Pena Nieto to prioritize protection for the media in the last year of his government, after at least 21 journalists were slain in the past decade with 'complete impunity.' 'The pursuit of justice has failed categorically,' CPJ said in a report on Mexico. 'The system seems to be corrupt down to its very foundation; either that or it's simply incapable of achieving justice.' Mexico, where battles among rival drug cartels have left tens of thousands dead in recent years, has the sixth worst record in the world for resolving the murders of journalists, according to the CPJ. Despite promises of action by Pena Nieto and his predecessors Felipe Calderon and Vicente Fox, Mexico's impunity rating has more than doubled since 2008, it added. The CPJ's impunity index is based on unsolved journalist murders as a percentage of a country's population. The drug-ravaged state of Veracruz is now the deadliest region for the media in the Western hemisphere, the CPJ said. CPJ said at least six journalists were murdered in retaliation for their work in Veracruz and three more went missing during the 2010 to 2016 administration of former governor Javier Duarte, recently detained in Guatemala over corruption allegations he denies. The group said it was investigating at least 11 more cases in the state to determine if journalists were murdered over their work. A special prosecutor's office tasked with crimes against freedom of expression has failed to produce convictions needed to deter future attacks, CPJ said. The impunity fosters self-censorship among journalists and corruption among public officials, CJP said. 'At a time when transparency and accountability have become a priority globally, the fact that this country has lagged behind has allowed the spread of untouchable governors, wealthy police officers who bury the truth, and mercenaries at the service of the drug trade that buys protection,' CJP said.