ANKARA (Reuters) - A prominent Turkish journalist denied on Wednesday that he sent out subliminal messages to coup plotters who tried to overthrow President Tayyip Erdogan last year, saying he had been put on trial for a crime which did not exist.

Turkish President Tayyip Erdogan makes a speech during a fast-breaking iftar dinner at the Presidential Palace in Ankara, Turkey, June 20, 2017. Yasin Bulbul/Presidential Palace/Handout via REUTERS

Mehmet Altan, an economics professor and journalist, and his brother Ahmet were detained in September and charged with giving coded messages in a television talk show a day before the abortive July 15 military coup, according to state media.

The brothers both face potential life sentences if convicted in their trial, which opened this week.

They have denied the charges, saying it was ridiculous to interpret their comments in the program - during which Mehmet Altan talked about the long history of military involvement in Turkish politics - as incitement to overthrow the government.

“If Rousseau were alive today and had shared his views on TV, he would be taken into custody for giving subliminal messages,” Altan told the court, referring to enlightenment philosopher Jean-Jacques Rousseau.

“There were no subliminal messages on that TV program... I have been detained for a non-existent message, over a non-existent crime,” he said according to a copy of his defense statement posted online.

The government blames followers of U.S.-based cleric Fethullah Gulen for masterminding the coup, and has waged a crackdown on suspected Gulen supporters since then.

Some 150,000 police, soldiers, judges and civil servants have been sacked or suspended, drawing criticism from rights groups and Western allies who fear an attempt to silence dissent. Tens of thousands of people have been arrested.

Turkish officials reject the criticism, saying the extent of the crackdown is justified by the gravity of the threat to the Turkish state in the wake of the coup attempt, when soldiers commandeered tanks and fighter jets, bombing parliament and other key buildings in an attempt to seize power.

Gulen has denied any involvement in the failed coup, and Altan said he had no knowledge of it.

“Surely I wasn’t aware of the coup attempt. I know that I stand here today just because I did not applaud the slaughter of democracy by the government,” he told the court.

Rights groups have voiced concerns over the trial of the Altans, who are among 100 journalists detained in the last year.

“There is no possible causal link between the defendants’ news articles and the failed coup of July 2016,” said Gabrielle Guillemin from the British rights group Article 19, adding that the charges were part of a “politically motivated campaign of harassment against journalists and other dissenting voices”.

The TV show’s presenter, Nazli Ilicak, a journalist, columnist and former lawmaker, was also arrested. “I am not an enemy of Erdogan. I am just an opponent. Is it a crime to oppose?” Ilicak told the same court a day earlier.

More than 200 writers worldwide, including Margaret Atwood, Russell Banks and JM Coetzee, and other public figures have signed a petition protesting against the arrests of the Altans.

In his comments on the television program the day before the coup attempt, Mehmet Altan referred to “another structure” within the Turkish state which he said was closely watching developments.

“It is not certain when it will take its hand out of the bag and how it will take its hand out of the bag,” Altan had said.