N'Djamena - Chadian unions and rights groups on Friday pulled out of several state institutions, including the election commission, saying they felt "gagged" in the run-up to closely-watched presidential polls.The announcement of the groups' withdrawal from Chad's electoral commission and other bodies comes a day after the trial of four leading activists held on controversial charges of disturbing the peace was postponed, prolonging their detention."Given the decision to maintain our comrades in detention, we have decided to withdraw" delegates from forums including the CENI (electoral commission), Goukouni Vaima, the deputy head of the UST labour federation, told a press conference.Oil-rich Chad, whose people are among the poorest in the world, has faced unprecedented protests in recent weeks as longtime leader Idriss Deby Itno seeks to extend his 26-year rule."We feel gagged," Vaima said, vowing that a protest march planned for April 5 would go ahead, despite a government ban on the rally.Vaima said the UST and three allied protest movements called "That's Enough", "Too Much Is Too Much" and "We're Tired" (Iyina in Chadian Arabic) were also pulling out of Chad's economic and social council, oil revenue transparency watchdogs and a forum for political dialogue.The four activists on trial in the capital N'Djamena were arrested ten days ago for calling for protests against Deby's administration.The spokesperson for the "Ca suffit" ("That's Enough") coalition, Mahamat Nour Ahmed Ibedou, was the first of the four to be arrested, followed by UST general secretary Younous Mahadjir, Nadjo Kaina Palmer, spokesperson for "Iyina" and the spokesperson for the "Trop, c'est trop" ("Enough is Enough") coalition. Celine Narmadji.Within minutes of their trial opening on Thursday it was postponed until April 7.Anger at the government was already running high following the gang rape in February of a young woman by the sons of several leading officials who posted images of her on Facebook, naked and crying. The video triggered nationwide student protests.Police and soldiers have cracked down hard on the demonstrations, killing two youths. At the end of February, a strike brought many towns across the country to a virtual standstill.Deby, a former armed forces chief turned warlord who seized power in 1990, faces 13 challengers for the presidency. The first round of voting takes place on April 10.In 2004, the constitution was modified to abolish a two-term limit on presidential mandates. Deby was declared the winner of elections in 2006 and 2011 by a huge majority.