A court in Turkey has charged three people with "terrorist propaganda", including a representative of Reporters Without Borders (RSF), BBC News reports.
It ordered the arrest of RSF representative Erol Onderoglu, journalist Ahmet Nesin and academic Sebnem Korur Fincanci.
RSF said it was "an unbelievable low for press freedom in Turkey".
The arrests come despite the EU pressuring Ankara to stop prosecuting academics and journalists.
The three had reportedly participated in a solidarity campaign in support of Ozgur Gundem, a pro-Kurdish newspaper.
Turkish media say they each acted as chief editor for a day.
Turkey is waging a military offensive against the Kurdistan Workers' Party (PKK) in the south-east and is restricting the press coverage of the campaign.
Several foreign journalists have been also arrested and deported for reporting the offensive.
The EU wants Turkey to change its terrorism laws, and has made it one of the conditions of its controversial migrant deal with Turkey that promises visa-free access to the EU for Turks.
