Burundi prosecutors Monday sought 15-year jail terms for four reporters and their driver who were detained covering an incursion of rebels from Democratic Republic of Congo and charged with endangering state security.The journalists were working for Iwacu, one of Burundi's few independent media outlets when they were arrested on October 22.A witness in the northwestern province of Bubanza, where they were arrested, told AFP on condition of anonymity the long jail terms were sought after two hours of deliberations.The source said the prosecution based the hefty sentencing demand largely on a WhatsApp exchange of messages between one of the reporters and a colleague based abroad in which the former wrote: "We are heading for Bubanza ... to help the rebels."A further demand was for the detained to be denied their civic rights for 20 years.Judgement was stayed for one month."We had the time to assure our clients' defence. We hope they will be acquitted purely and simply," defence counsel Clement Retirakiza, told reporters.Police say at least 14 rebels from the Burundian RED-Tabara group, based across the border in eastern DR Congo, were killed in an attack the day the journalists were arrested.The rebels say they killed a dozen security personnel.The Reporters Without Borders NGO, which places Burundi a lowly 159th on its global list of press freedom, says those detained were simply doing their job while Human Rights Watch has called for their release.Observers see the case against the four as a signal of toughness by the Burundi government just five months ahead of elections.The country is currently mired in violent unrest sparked by President Pierre Nkurunziza announcing in April 2015 he was controversially standing for a third term. He won re-election in the July.