A Turkish court on Tuesday remanded in custody seven journalists, including AFP photographer Yasin Akgul, who had been detained after covering the Istanbul protests that erupted after the arrest of the city's mayor.
The ruling reversed an earlier decision to grant them conditional release, their lawyers and the MLSA rights group said.
Akgul and his colleagues had all been arrested at their homes before dawn on Monday.
They were all charged with "taking part in illegal rallies and marches and failing to disperse despite warnings", court documents showed.
The court decision was slammed as "scandalous" by Reporters Without Borders (RSF), with the Turkish Photojournalists Union denouncing it as "unlawful, unconscionable and unacceptable".
Akgul, 35, was one of 10 Turkish journalists rounded up early on Monday after days of covering the mass protests that began in Istanbul and spread across Turkey following the March 19 arrest of the city's opposition mayor, Ekrem Imamoglu.
On Tuesday morning, he and six other journalists were taken to Cthe aglayan courthouse, where they were granted conditional release.
But in what legal observers described as an "unprecedented" U-turn, prosecutors suddenly revised their request and asked the court to order their formal arrest, Akgul's lawyer said.
Court documents seen by AFP said the move was necessary because there was a risk they could flee.
"Because of the existence of facts indicating that they committed the crime of which they are accused" and due to the possibility of a flight risk, "judicial supervision would be insufficient at this stage", the documents said.
Ahead of the decision there was an extremely tense atmosphere inside the courthouse, which was packed with families, including those of many detained students whose cases were also being heard, an AFP correspondent at the scene said.
"This is the first time that a clearly identified journalist has, in the exercise of his duties, been formally arrested on the basis of this law against gatherings and demonstrations," RSF's Erol Onderoglu told AFP, following the decision about Akgul, the first to be made.
"This scandalous decision reflects a very serious situation in Turkey."