In the dock were 189 suspects who were rounded up in a government crackdown on the protests, which erupted following the March 19 detention and subsequent jailing of Istanbul's opposition mayor Ekrem Imamoglu.

As the trial opened, the Caglayan courthouse was packed with family members, journalists, university lecturers and lawmakers from the main opposition CHP party, an AFP correspondent said.

Most of the defendants were students, but among them were also eight Turkish journalists, including AFP photographer Yasin Akgul, who had been covering the biggest wave of street protests to grip Turkey since 2013. 

The suspects are facing a number of charges, notably "taking part in illegal rallies and marches" and "failing to disperse despite police warnings"; offences that could carry between six months to four years behind bars.

Addressing the court on behalf of the journalists, lawyer Veysel Ok called for their acquittal on the grounds that they were reporting the news of the demonstrations.

"They were there as journalists to cover the protests [...] that's what they are paid for," he told the judge.

The judge rejected the acquittal request but agreed to separate their file from that of the students.

According to the indictment, their claim to be journalists "has not been counted" because the police did not establish that they were present for journalistic purposes. 

"We want the journalists to be acquitted" because they are being tried on the basis of false evidence, Erol Onderoglu, the Turkey representative of Reporters Without Borders (RSF) told AFP. "Unfortunately, their prosecution is as arbitrary as their detention and arrest."

'Justice for our children'

For most of the youths, it was the first time they had joined a protest, as large-scale rallies have been largely non-existent since a government crackdown on the 2013 Gezi Park protests. 

"We want justice for our children. They need to be at their desks in university, not in prison," Avni Gundogdu, co-founder of The Parents' Solidarity Network, told AFP outside the court. 

The Istanbul prosecutor's office said 819 people will be tried in 20 criminal investigations. 

In a statement, Human Rights Watch criticized the "rushed nature and mass scale of the trials", saying it had reviewed nine indictments involving 650 defendants but found the charges "lack evidence of criminal wrongdoing". 

"Given the glaring absence of evidence, it is hard not to conclude that the intended purpose of these rushed trials is to send a warning against exercising the rights to peaceful protest or free expression," said HRW's Europe and Central Asia director Hugh Williamson. 

Istanbul's jailed mayor is President Recep Tayyip Erdogan's greatest political rival, and his arrest sparked protests that spread across the country, despite a ban on demonstrations in Turkey's three largest cities.

Police cracked down using teargas, pepper spray and rubber bullets to disperse the crowds, and rounded up nearly 2,000 people, many during pre-dawn home raids. 

Social media posts

HRW said 62 of those in court Friday were charged with carrying weapons or hiding their faces to avoid being identified "yet the only specifics provided [was] an allegation that one protestor had a rock in his hand." 

Another 20 were charged with seeking to "incite a crime". 

But HRW said that "overwhelmingly" involved social media posts encouraging the public "to join people in the streets and statements against the government, and not calls for violence or criminality". 

The next hearing will take place on Oct. 3, according to court documents, without giving a date for when the journalists' case would be heard. 

With many family members unable to enter the courthouse due to tight security, hundreds protested by the metal barriers outside, closely watched by an army of police, an AFP correspondent said.

"We are here for the trials of our friends who are in custody. We won't leave them on their own," a student called Ahmetcan Kaptan told AFP.