Turkey's state-run news agency says prosecutors are seeking maximum 15-year prison terms for five journalists of an opposition newspaper, intensifying concerns over authorities' crackdown on news coverage critical of the government.

Anadolu Agency reported Monday that prosecutors are accusing Sozcu newspaper columnists Emin Colasan and Necati Dogru as well as three editors of aiding a network led by U.S.-based Muslim cleric Fethullah Gulen, without being a member of his movement.

The five will stand trial in Istanbul on Jan. 18.

Turkey accuses Gulen of orchestrating a failed military coup in 2016 and has branded his network a terror organization. Gulen denies involvement.

The journalists are accused of supporting his group through their writings in Sozcu.

The Turkish Journalists' Syndicate says that about 145 journalists are currently in jail.