Egyptian authorities on Sunday freed a prominent secular activist but extended the detention of another after the two were arrested for holding unauthorised demonstrations, judicial sources said. Ahmed Maher, founder of the April 6 movement which was one of the main groups that spearheaded the revolt against Hosni Mubarak in 2011, had been released, the sources said. But Alaa Abdel Fattah, another prominent secular activist who had been arrested at his home late Thursday, was being detained for another 15 days, they said. Maher had turned himself in at a Cairo court on Saturday. Both of the activists had been ordered arrested for holding unauthorised demonstrations in Cairo this week. Abdel Fattah's detention was extended because he was accused of breaking a law on demonstrations, inciting protesters to riot, and cutting of roads and beating a police officer. Egyptian authorities say their demonstrations were unauthorised according to the law passed by the interim president Adly Mansour on November 24 which bans all gatherings held without obtaining prior permissions. Abdel Fattah held a demonstration against a provision in the draft charter allowing military trials of civilians. The provisions concerning the military's powers and privileges will be under focus Sunday when a 50-member panel that drafted the new charter meets to vote on it.