Turkish police on Saturday detained a veteran journalist and his academic brother as part of the investigation into the failed July 15 coup, the latest prominent figures to be detained in the controversial crackdown after the putsch.

Journalist and writer Ahmet Altan and his brother, Professor Mehmet Altan, were detained early in the morning by Istanbul anti-terror police, the state-run Anadolu news agency reported.

The Dogan news agency said they were detained in the investigation into the July 15 coup, which Ankara blames on the US-based Islamic preacher Fethullah Gulen.

Ahmet Altan, a hugely prominent figure in Turkey, 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 is the author of several books on politics in Turkey.

The Hurriyet daily said that 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.

The TV channel, seen by the authorities as staunchly pro-Gulen, has since been shut down.

Turkey has detained dozens of journalists in the wake of the coup, raising accusations from rights groups of a drastic erosion of press freedoms. But the government says those accused were not engaged in normal journalistic activity.

Among those arrested previously is 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.

Gulen had over the last years built up a substantial media presence in Turkey, with prominent newspapers such as Zaman, English-language Today's Zaman and TV channels like Samanyolu all closely linked to him. They have since been shut down.

The cleric, who has lived in the United States since 1999, strongly denies any involvement in the coup.