Condemnation grows over Turkey's widening crackdown

"Targeting one of Turkey’s last independent opposition newspapers with ludicrous charges shows the depths of the Turkish government and president’s crackdown," said Emma Sinclair-Webb, Turkey director at Human Rights Watch.

"Over 160 media outlets have been closed down since the failed coup, and there are few critical voices that have not been ruthlessly silenced."

The Cumhuriyet, which had published revelations embarrassing for the government, said at least a dozen journalists and executives were detained in early morning raids.

The raids came after authorities fired more than 10,000 civil servants at the weekend, closed 15 pro-Kurdish and other media outlets, and arrested two mayors in the south east of the country, the latest purge since July's failed military coup aimed at ousting Erdogan.

"The jailing of Gültan Kışanak and Fırat Anlı without credible evidence of criminal wrongdoing is the most dramatic evidence to date of the government’s willingness to deny the people of southeastern Turkey the right to democratically-elected political representatives," Sinclair-Webb said.

Jailing elected mayors and the assault on independent media seriously call into question whether Turkey's political leaders have any regard for basic democratic principles

"Jailing elected mayors and the assault on independent media seriously call into question whether Turkey’s political leaders have any regard for basic democratic principles."

Cumhuriyet's editor Murat Sabuncu was detained and police were hunting for executive board chairman Akin Atalay, the official news agency Anadolu said.

The Istanbul prosecutor said an investigation had been launched into allegations the secular daily's output was "legitimising" the attempted putsch.

The newspaper said it would "fight until the end for democracy and freedom" in a statement on its website headlined: "We will not surrender".

"Cumhuriyet is a newspaper and being a journalist is not a crime," it added. "Believing in its journalism, it continues and will continue its publication."

Cumhuriyet is a newspaper and being a journalist is not a crime... Believing in its journalism, it continues and will continue its publication

Cumhuriyet said an arrest warrant was also issued for former editor-in-chief Can Dundar, who was sentenced to jail in May for allegedly revealing state secrets in a high-profile case that triggered alarm about the state of press freedom in Turkey.

The newspaper had accused the government of seeking to illicitly deliver arms bound for Islamist rebels in Syria. Erdogan had warned Dundar that he would "pay a heavy price".

Dundar is now believed to be in Germany after he was freed earlier this year pending appeal.

He described Monday's actions as the "storming of the last fortress" as Turkish media said his house in Istanbul was also raided.

The International Press Institute said an arrest warrant was issued for one of the rights group's board members, Kadri Gursel, who also wrote for Cumhuriyet.

'Media cannot be silenced'

Washington also issued a stern rebuke to its ally after the latest move and criticised Ankara's ongoing detention of many journalists.

"The United States is deeply concerned by what appears to be an increase in official pressure on opposition media outlets in Turkey," US State Department spokesman John Kirby said.

"Democracies become stronger by allowing diverse expressions of views, particularly in difficult times," he added.

Democracies become stronger by allowing diverse expressions of views, particularly in difficult times

In a move heavily criticised by Western leaders and rights groups, tens of thousands of civil servants, soldiers, police, judges and teachers have been suspended, fired or detained since the attempted coup, blamed on exiled Muslim cleric Fethullah Gulen.

The Istanbul prosecutor said in a statement quoted by media that Cumhuriyet and its owner the Cumhuriyet Foundation were being investigated over whether they committed crimes on behalf of Gulen's movement or the outlawed Kurdistan Workers' Party (PKK).

But the prosecutor said those investigated were not accused of being members of either group.

Dozens of demonstrators gathered outside Cumhuriyet's Istanbul offices to protest the detentions, waving copies of Monday's paper which bore the headline: "Again, a coup against opposition".

"A free media cannot be silenced," they chanted.

Monday's edition of the paper criticised the government's weekend announcement of the closure of several media outlets as well as the suspension of university rector elections.

What is happening is ridiculous. You will not scare anyone with this repression

Erdogan is set to pick the winners from a pool of candidates selected by the nation's education authority.

Turkish Deputy Prime Minister Numan Kurtulmus insisted the investigation was not targeting journalists but probing the Foundation.

Council of Europe chief Thorbjorn Jagland also criticised the raids, saying it was "highly questionable if the raid against Cumhuriyet can be justified as a proportionate measure, even under the state of emergency".

European Parliament President Martin Schulz said the "ongoing massive purge" seemed to be "motivated by political considerations, rather than legal and security rationale".

Cumhuriyet cartoonist Musa Kart meanwhile described his detention as "ridiculous".

"Until today, I have drawn hundreds and thousands of caricatures of the (Gulen movement) and PKK... What is happening is ridiculous. You will not scare anyone with this repression."

Agencies contributed to this report