Al Jazeera on Thursday marked 1,000 days since its producer Mahmoud Hussein was detained in Egypt following accusations of incitement against the state and spreading false news.
Al Jazeera has been caught up in the political rift between Cairo and Doha following the 2013 military ouster of Islamist president Mohamed Mursi.
Staff at the network marked the milestone by wearing badges and T-shirts calling for Hussein's release, as well as gathering in the newsroom of the flagship Arabic channel during live broadcasting.
"His family needs to know that we are supporting him and we are with him and we are not going to forget him. We keep fighting until he is out," Al Jazeera Media Network acting director general Mostefa Souag told AFP.
"It doesn't seem that the Egyptian government listens to reason or to the law or to the rules of the constitution itself."
Al Jazeera is seen by Egypt's government as a mouthpiece for Mursi's outlawed Muslim Brotherhood group. Access to its website has been blocked in Egypt since 2017.
Hussein was arrested during a personal visit to Cairo in late December 2016 and charged with several crimes.
Prosecutors ordered his release in May, but a week later he was hit with another set of charges and detained once again.
Shortly after Mursi's removal by the military in 2013, authorities arrested three other Al Jazeera journalists, including an Egyptian-Canadian and an Australian, provoking international condemnation.
The three journalists, who faced accusations similar to those levelled against Hussein, were freed in 2015.
Australian journalist Peter Greste was deported and the two others were released after receiving pardons from President Abdel Fattah al-Sisi.
In June 2017, Egypt — along with Saudi Arabia, the United Arab Emirates and Bahrain — severed ties with Qatar over allegations that it supports "terrorist" groups, including the Brotherhood.
Rights groups regularly accuse Sisi's regime of crushing dissent and repressing its political opponents.
Under his rule, authorities have jailed thousands of Morsi's Islamist supporters as well as liberal and secular activists, including popular bloggers, actors, singers and journalists.