Maher and Douma, as many other liberal activists, supported the campaign for Morsi to leave office, but have since been voicing their disapproval of what they see as the return of Mubarak-era police brutality and the curtailment of the freedom of expression.
The proceedings against the two also come days after a 50-member panel appointed by the interim president finished extensive amendments to an Islamist-tilted constitution adopted last year. However, the new document allows the trial of civilians before military courts in a wide range of cases and gives the military the exclusive right of appointing the defense minister for eight years starting from the election of the next president.
The government's campaign for a "yes" vote in a referendum to be held soon was given a massive boost when a major ultraconservative Islamist party, Al-Nour, announced on Thursday its backing for the amended charter and called on its followers to vote for the document.
Al-Nour's leader, Younis Makhyoun, told a news conference that the party's decision was designed to "safeguard the nation's interests, ensure its progress and prosperity and to spare it more chaos."
Al-Nour, which is at odds with the Brotherhood, led a coalition of Salafi parties that won about 25 percent of the vote in a parliamentary election held in late 2011 and early 2012.