Nobel-winning Turkish writer Orhan Pamuk on Sunday lashed the arrest of a leading journalist and warned Turkey was heading towards "a regime of terror."
"In Turkey, we are progressively putting behind bars all people who take the liberty of voicing even the slightest criticism of the government," Pamuk said.
The crackdown is being driven by "the most ferocious hatred," he added.
"Freedom of thought no longer exists. We are distancing ourselves at high speed from a state of law and heading towards a regime of terror," Pamuk said bluntly.
His front-page opinion piece was published by La Repubblica newspaper a day after the dawn detention of prominent journalist Ahmet Altan and his brother Mehmet Altan, a renowned academic and economist.
Pamuk, who won the Nobel Prize for literature in 2006, was a known critic of President Recep Tayyip Erdogan before the attempted coup against the Turkish strongman in July.
He called for all detained intellectuals to be released "as soon as possible" and to stand trial on the basis of free individuals.
Police arrested the two Altan brothers on Saturday as part of an investigation into the failed July 15 coup, the state-run Anadolu news agency reported.
Ahmet Altan was for years a columnist with top dailies like Hurriyet and Milliyet before in 2007 founding the opposition daily Taraf.
He resigned his post as Taraf editor-in-chief in 2012 and has also written several novels.
Mehmet Altan, an economist by training, is the author of several books on politics in Turkey.
The Hurriyet daily said the Altan brothers were investigated over comments in a talk show on the Can Erzincan TV channel on July 14, on the eve of the coup.
Erzincan is seen by the authorities as being staunchly in favour of US-based preacher Fethullah Gulen, whom they blame for the attempted putsch. The channel has since been shut down.
Other arrests include veteran journalist and writer Nazli Ilicak, who also appeared on the same talk show with the Altan brothers.
The content of the talk show has not been publicised in Turkish media.