Turkish courts have ordered a media blackout on reporting the detention of the editor-in-chief of secularist opposition newspaper Cumhuriyet.
Murat Sabuncu was detained while authorities searched for executive board chairman Akin Atalay and writer Guray Oz, the official news agency Anadolu said.
Police were searching the homes of Mr Atalay and Mr Oz, the agency added.
CNN Turk said police have issued detention warrants for 13 of the paper's journalists and executives.
The media blackout prohibits the press from reporting on the detention of Cumhuriyet journalists.
The detentions are the latest in a massive crackdown following a failed coup in July by a rogue faction of the military to oust President Recep Tayyip Erdogan.
Tens of thousands of civil servants have since been suspended, fired or detained, with the government blaming the coup bid on exiled Muslim preacher Fethullah Gulen.
The government has also shut more than 100 media outlets and detained dozens of journalists as it presses a purge that has been criticised by Western leaders and human rights organisations.
Mr Sabuncu's arrest also came as the government fought an insurgency from the outlawed Kurdistan Workers' Party (PKK).
The government's operation against Cumhuriyet was launched over its alleged "activities on behalf of" the Gulen movement and the PKK.
The PKK - proscribed as a terrorist organisation by Ankara, the EU and the US - has waged an insurgency in Turkey since 1984.
Cumhuriyet's former editor-in-chief Can Dundar was sentenced in May by a Turkish court to five years and 10 months in prison for allegedly revealing state secrets.
Mr Dundar is now believed to be in Germany after he was freed earlier this year pending an appeal.
Additional reporting by agencies
