If convicted, prosecutors said in an indictment they want publisher Ragip Zarakolu to be sentenced to 10 years in prison, and political scientist Busra Ersanli to be sentenced to 15 years, state news agency Anatolia said.

The two men were arrested and jailed in November, provoking widespread protests in Turkey and overseas.

Zarakolu, the recipient of the 2008 Freedom to Publish Prize of the International Publishers Association and a freedom of expression activist, was also a columnist for the dissident daily Ozgur Gundem, a pro-Kurdish newspaper. He has been charged with supporting a terrorist organisation.

Ersanli, a constitutional expert, is accused of being the head of a terrorist organisation.

In all, 193 suspects face trial in the investigation.

Turkey has carried out several major operations in recent years as part of a clampdown against the Union of Kurdish Communities (KCK).

The KCK is a clandestine group suspected of being the political wing of the armed Kurdistan Workers Party (PKK). Authorities accuse the KCK of wanting to promote insurrection in Turkey's Kurdish regions.

The PKK, listed as a terrorist group by Ankara and much of the international community, took up arms in Kurdish-majority southeast Turkey in 1984, sparking a conflict that has claimed about 45,000 lives.

The Turkish government says that 700 people have been jailed for colluding with the KCK since 2009. Kurdish media put the number much higher, at 3,500.