A Turkish court on Friday ordered civil society leader Osman Kavala to remain in jail pending trial on charges that rights groups say are part of President Recep Tayyip Erdogan's bid to stifle dissent.

The presiding judge rejected a defence request to release the 63-year-old -- in custody without a conviction for more than three years -- and set a trial date for February 5.

US academic Henri Barkey is being tried in absentia alongside Kavala in a case linked to the 2016 failed coup attempt against Erdogan.

"I have opposed military coups my entire life and have criticised the army's interference in politics," Kavala told the court by video link as his wife watched from the courtroom.

"These (accusations) are in stark contrast to my worldview and ethical values."

Rights groups view Kavala's fate as a bellwether regarding freedom of expression under Erdogan -- a strong-willed leader who has ruled Turkey as prime minister and president since 2003.

The Parisian-born businessman was a founding member of philanthropist George Soros' Open Society Foundation in Turkey and headed a group that promoted cross-cultural ties through the arts at the time of his arrest.

Kavala has remained in prison despite being acquitted in February in connection with 2013 protests about the planned demolition of an Istanbul park that morphed into the first serious challenge to Erdogan's rule.

He was re-arrested before he could return home on fresh charges of espionage and attempting to overthrow the constitutional order in the failed 2016 coup.

Kavala termed his detention immediately after acquittal "moral torture".

His court appearance Friday was accompanied by a wave of speculation about a possible easing of political and legal pressure on Erdogan's longstanding foes.

Erdogan was forced to part ways last month with his powerful son-in-law -- once viewed as the president's second-in-command -- and appoint a more market-friendly team to tackle Turkey's growing economic problems.

He promised to launch judicial reforms at the same time to attract foreign investors who have grown disillusioned about the state of Turkey's rule of law.

Turkish businessman and philanthropist Osman Kavala's trial is seen by rights groups as a bellwether on the state of freedom of expression under President Recep Tayyip Erdogan
Turkish businessman and philanthropist Osman Kavala's trial is seen by rights groups as a bellwether on the state of freedom of expression under President Recep Tayyip Erdogan AFP / OZAN KOSE

The change in tone prompted former deputy prime minister and Erdogan ally Bulent Arinc to say he was "shocked by the fact that (Kavala) is still under arrest".

Erdogan distanced himself from the comments a few days later and Arinc was forced to resign from the president's advisory body.

Kavala's supporters are also pinning their hopes on a constitutional court hearing of his appeal for an immediate release. It is unclear when a ruling will be announced.

"We hope that... the constitutional court will urgently review Kavala's application and stop this mockery of the judicial process once and for all," the European Parliament's Turkey rapporteur Nacho Sanchez Amor said.

"The continued backsliding in the field of rule of law and fundamental rights remains, in our view, the main obstacle to progress in any positive agenda that the EU could offer to Turkey."

Kavala would be sentenced to life in prison if convicted of trying to overthrow the constitutional order. The espionage charge carries an additional 20 years in jail.

His case is being heard alongside that of Turkish-born US academic Barkey -- a former member of the State Department Policy Planning Staff who lives in the United States and is being tried in absentia.

The accusations against Barkey stem from a conference he organised about Iran on an island off Istanbul at the time of the 2016 coup attempt.

The charge sheet alleges Barkey used the event as cover to coordinate the putsch with Kavala.

The indictment includes data from cell phone receivers placing him and Kavala several times in the same areas of Istanbul.

Human rights defenders say such data are irrelevant and had already been ruled inadmissible by the constitutional court.

Barkey called the charges against him "a travesty of the first order".

"They do not and cannot have any evidence against me and so they are making it up," he told AFP in a statement.

George soros