ISTANBUL - Turkish authorities on Monday detained three prominent campaigners for press freedom, including the local representative of Reporters Without Borders (RSF), on charges of spreading terrorist propaganda, human rights groups said.The arrests will further stoke fears for media freedoms in Turkey under President Tayyip Erdogan following a series of high-profile cases against opposition newspapers and broadcasters.The three detainees are RSF representative Erol Onderoglu, author Ahmet Nesin and Sebnem Korur Fincanci, the president of the Human Rights Foundation of Turkey. They were sent to pre-trial detention after they guest-edited a magazine on Kurdish issues and campaigned against efforts to censor it, said RSF and another group, EuroMed Rights.Onderoglu was arrested for his work on three articles about security operations in Turkey's largely Kurdish southeast and infighting among security forces which appeared in the May 18 edition of the Ozgur Gundem magazine, said Johann Bihr, from RSF.Bihr described Onderoglu, who had worked for RSF for two decades, as a "victim of the abuses he always denounced".An official at Erdogan's office declined to comment on the cases. It was unclear how long the three would be detained or when they would face trial. Last month Turkey came under fire for sentencing two prominent journalists at the opposition Cumhuriyet newspaper to at least five years in jail for revealing state secrets in a case in which Erdogan was named as a complainant.Turkish authorities have also seized or shut down several newspapers and taken broadcasters off the air in the last year, usually citing security concerns. They deny trying to muzzle free expression.Turkey's record on press freedoms and broader human rights has increased reservations among some European politicians about whether Turkey, a NATO member, is a suitable candidate for membership of the EU.But their criticism has been relatively muted in recent months because the EU needs Turkey's close cooperation in curbing the flow of illegal migrants into Europe.Under a deal agreed in March, Turkey is set to benefit from speedier EU accession talks and visa free access to Europe for its citizens if it takes back all migrants and refugees who cross the Aegean to Greece illegally.