Seventeen employees of a Turkish opposition newspaper went on trial today accused of aiding a terrorist organisation.

The hearing coincides with an escalating dispute with Germany over the arrest in Turkey of 10 rights activists, including one German, as part of a crackdown since last year’s attempted coup against President Tayyip Erdogan.

The case is seen by government critics as a further sign that freedom of expression is under attack.

“Journalism is not a crime,” chanted several hundred people gathered outside the central Istanbul court to protest against the prosecution of writers, executives and lawyers of the staunchly secularist Cumhuriyet newspaper.

Turkish prosecutors are seeking up to 43 years in jail for staff from the paper, including some of Turkey’s best-known journalists, who are accused of targeting Erdogan through “asymmetric war methods”.

What exactly they are charged with however remains unclear. According to Anadolu, the state news agency, the charges brought against them include supporting the movement around the preacher Fethullah Gulen and the banned Kurdistan Workers’ Party or PKK.

Anadolu does not provide details on more concrete accusations such as the form this support is alleged to have taken.

Cumhuriyet’s former chief editor Can Dundar, is living in Germany, is being tried in absentia.

“I´m proud of my friends in jail still resisting and defending the paper and their rights to express themselves and defending the truth,” he said.

The newspaper has called the charges “imaginary accusations and slander”. Social media posts comprised the bulk of evidence in the indictment, along with allegations that staff had been in contact with users of Bylock, an encrypted messaging app the government says was used by Gulen’s followers.

Rights groups and Turkey’s Western allies have complained of deteriorating human rights under Erdogan. In the crackdown since last July’s failed coup, 50,000 people have been jailed pending trial and some 150,000 detained or dismissed from their jobs.

As part of the purge some 150 media outlets have been shut down and around 160 journalists are in jail, according to the Turkish Journalists’ Association.

The crackdown has strained Turkey’s ties with the European Union, but reaction from the bloc has been restrained because it depends on Turkey to curb the flow of migrants and refugees into Europe.

Turkish authorities say the crackdown is justified by the gravity of the coup attempt, in which rogue soldiers tried to overthrow the government and Erdogan, killing 250 people, most of them civilians.