The indictment is the second against Demirtas, a former co-leader of the Peoples’ Democratic Party (HDP) and presidential candidate, related to October 2014 protests in the mainly Kurdish southeast.
Thirty seven people died in clashes during the protests, which began over accusations that the army stood by as Islamic State militants besieged the Syrian Kurdish town of Kobani, in plain view just across the Turkish border.
An indictment calling for 38 counts of life sentences without parole against 108 defendants, including Demirtas, was accepted by an Ankara court on Thursday, state-owned Anadolu agency said.
It reported last week that the charges included 37 cases of homicide and disrupting the unity and territorial integrity of the state.
Of the defendants, 27 are jailed pending trial, 75 have arrest warrants against them and six were detained then released with judicial measures, state broadcaster TRT Haber said.
Last month the ECHR called for Demirtas’ release, saying the justification for holding him for more than four years in prison was a cover for limiting pluralism and debate and the evidence did not back up the terrorism-charges directed at him.
While ECHR decisions are binding, Turkey has ignored several recent rulings. President Tayyip Erdogan accused the ECHR of hypocrisy after the ruling, saying Demirtas was a terrorist responsible for the deaths of tens of people.
Demirtas has faced several trials on different charges.
In 2019 a court lifted an arrest warrant in the first case related to the Kobani protests, while another agreed to release Demirtas given time already served from a previous sentence. But a new arrest warrant related to the same events in 2014 kept him in jail.
The ECHR said his continued detention on such similar grounds would amount to a “prolongation of the violation of his rights.”
Turkish authorities said the militant Kurdistan Workers Party (PKK) - designated a terrorist group by Turkey, the United States and the European Union - incited the protests and that the HDP supported them. The HDP, Turkey’s third largest party, denies links to terrorism.
The PKK took up arms against the Turkish state in 1984 and more than 40,000 people have been killed in the conflict.