ISTANBUL: Four Turkish academics go on trial Friday for “terrorist propaganda” in the latest of a series of court cases that have highlighted growing restrictions on free speech under President Recep Tayyip Erdogan.

Across town, journalists accused of divulging state secrets also return to court for the third hearing of their Istanbul espionage trial.

The university scholars are being prosecuted for signing a petition along with over 1,000 colleagues and supporters denouncing the government's military operations against Kurdish rebels in the country's southeast.

Demonstrators were expected to protest in Istanbul ahead of the trial, set to begin at 2pm (1100 GMT).

The petition urged Ankara to halt “its deliberate massacres and deportation of Kurdish and other peoples in the region”, infuriating President Recep Tayyip Erdogan, who said the dons had fallen into a “pit of treachery”.

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The four are accused of engaging in “terrorist propaganda” and “inciting hatred and enmity” for not only signing the plea but making a statement on the same lines on March 10, a day before the petition was published.

If convicted, Esra Mungan Gursoy, Meral Camci, Kivanc Ersoy and Muzaffer Kaya face up to seven and a half years behind bars, according to Academics for Peace (BAK), the organisation behind the contested statement.

Turkey is waging an all-out offensive against the separatist Kurdistan Workers' Party (PKK), with military operations backed by curfews aimed at flushing out rebels from several southeastern urban centres. But Kurdish activists say dozens of civilians have died as a result of excessive force.

The decision to haul scholars and journalists into court has deepened unease over freedom of expression under the increasingly autocratic Erdogan.

The US and European Union have already expressed concern over the trial of two journalists of the Cumhuriyet newspaper for publishing articles alleging the government delivered weapons to militants in Syria.

Their closed-door trial enters a third day Friday, with the hearing expected to begin at 10am (0700 GMT).

Can Dundar, editor-in-chief of leading opposition daily Cumhuriyet, and Erdem Gul, his Ankara bureau chief face life in prison over a story accusing the government of seeking to illicitly deliver arms to rebels in Syria.