Turkey’s main opposition Republican People’s Party (CHP) staged mass rallies on June 15, the day after one of its deputies, Enis Berberoglu, received a 25-year prison sentence for revealing state secrets. Berberoglu, a journalist by profession and former editor-in-chief of Hurriyet, the country’s largest newspaper, was immediately placed in custody and taken to Maltepe Prison in Istanbul.

Although he is the first CHP deputy to be imprisoned in 15 years of Justice and Development Party (AKP) rule, Berberoglu joins about a dozen other primarily Kurdish Peoples’ Democratic Party (HDP) deputies who are serving prison terms, including co-chairman Selahattin Demirtas.

In response, CHP chairman Kemal Kilicdaroglu called for a “Justice March” that drew thousands of people. The leader of Turkey’s secular opposition party aims to walk from the capital, Ankara, to Istanbul’s Maltepe district, where Berberoglu is held, a distance of some 430 kilometers (about 267 miles) that Kilicdaroglu plans to walk in 20 days.

After the criticism for his timid response to Turkish President Recep Tayyip Erdogan’s increasing authoritarianism and fraud allegations in the April 16 referendum, Kilicdaroglu’s recent move has received positive coverage in the domestic and international media.