Two weeks after an Istanbul court denied an appeal against journalist Deniz Yucel's detention, his lawyers on Wednesday took the case to the Constitutional Court in Ankara, Turkey's highest court.

According to German newspaper "Die Welt," where Yucel's worked as a correspondent, lawyers submitted an application this week arguing that his imprisonment violated his physical integrity, personal freedoms, right to a fair trial, and right to freedom of expression, among other legal breaches.

Turkish authorities issued an arrest warrant against Yucel in February, charging him with spreading propaganda on behalf the banned Kurdistan Workers' Party (PKK) and cleric Fethullah Gulen's movement, as well as sedition. Yucel's lawyers also maintain that Yucel's writing is protected by Turkey's press freedom and freedom of expression law.

The 43-year-old journalist turned himself in to Istanbul police upon hearing that he was wanted by authorities. He remained in police custody for two weeks before a judge formally charged him with creating "terrorist propaganda."

Turkish President Recep Tayyip Erdogan has also accused Yucel of spying for the PKK with Germany's support.

In an interview with DW, one of Yucel's closest friends Doris Akrap reported that he was being kept in isolation and forbidden from any form of contact with the outside world except for with his direct family - who live in Germany - for one hour a week.

Germany denounces Yucel detention

Yucel's arrest and detention has sparked outcry in Germany and drawn sharp criticism from the German government. German President Frank-Walter Steinmeier last week called on Yucel to be released, while German Chancellor Angela Merkel characterized the decision to keep Yucel in investigative custody "bitter and disappointing." 

"This measure is disproportionately harsh, especially given that Deniz Yucel presented himself to the Turkish justice system voluntarily and for the purpose of the investigation," she said, adding that "the German government expects that the Turkish justice system keeps in mind the great importance that press freedom has in any democratic society in its treatment of the Yucel case."

Yucel's detention also led a number of German towns to cancel Turkish referendum rallies, worsening the dispute between Berlin and Ankara.

dm/bw (dpa, AFP)