Two Turkish journalists face life in prison over a story alleging that the Turkish government was arming Islamist militants in Syria.
Cumhuriyet newspaper’s editor-in-chief Can Dundar and its Ankara representative Erdem Gul have been charged with espionage.
Prosecutors accuse them of working with a US-based cleric to discredit the government.
Media freedom groups have condemned the charges.
Human Rights Watch said the two “were doing their job as journalists and no more than that”.
In its report last May, Cumhuriyet published video of police finding weapons in trucks that it said were linked to Turkish intelligence.
The Turkish authorities insisted the trucks, which had been intercepted near the Syrian border, were in fact bringing aid to Syria’s Turkmen minority.
But the report caused uproar and prompted President Reccep Tayyip Erdogan to file a lawsuit against the journalists.
Mr Erdogan said the video footage was a state secret and vowed on TV that the journalists “would pay a heavy price”.
The pair were detained in November and told the BBC they were kept in solitary confinement for 40 days before being allowed to share a cell.
The government accuses them of helping the Hizmet movement led by Fethullah Gulen, who lives in self-imposed exile in Pennsylvania.
Mr Erdogan has accused Mr Gulen of plotting against him, although Mr Gulen denies this.
Mr Dundar and Mr Gul are accused of working with Hizmet to create the impression that the Turkish government was helping terror groups, thus weakening its ability to rule.
They face charges of espionage, attempting to overthrow the government and support for a terror organisation, Hurriyet reported.
Turkey has come under mounting criticism for its treatment of journalists.
Last week, US Vice-President Joe Biden called on Turkey to protect freedom of expression during a visit to the country and also met with Mr Dundar’s wife in a show of support.
Freedom of the press in Turkey
- Turkey ranks 149th amongst the 180 countries in the Reporters Without Borders’ World Press Freedom Index 2015
- Media organisations in Turkey say that more than 30 journalists are currently behind bars
- Most are of Kurdish origin
- The government argues journalism in Turkey is among the most free in the world