Chad is to try 401 people detained during and after deadly anti-government protests last month, prosecutors said on Friday.
Officially, around 50 people -- including 10 members of the security forces -- died when police opened fire on the demonstrators in the capital N'Djamena and several other cities on October 20.
But opposition groups say the actual toll was much higher, with unarmed civilians massacred.
Prosecutors said the 401 detainees would be tried on Tuesday inside the high-security prison of Koro Toro in the middle of the desert, more than 600 kilometres (370 miles) northeast of the capital.
"The hearings will be held from November 29 to December 4," the N'Djamena prosecution said.
The 401 were being tried on several charges including taking part in an "unauthorised gathering", "destroying belongings", "arson", and "disturbing public order", it said.
Opposition groups had encouraged protests on October 20 to mark the date when the ruling military had initially promised to cede power -- a timeline General Mahamat Idriss Deby Itno has now extended by two years.
The 38-year-old took power from his father, Idriss Deby Itno, who ruled for 30 years before dying in an operation against rebels in April 2021.
The public prosecutor earlier this month said Chadian authorities has arrested 621 people, including 83 minors, after the protests, all of whom were transferred to the Koro Toro prison.
Beyond the 401 to stand trial Tuesday, investigations were ongoing for 220 other people, including 83 minors, the prosecution said.
Koulmen Nadjiro, the secretary of the Chad Bar Association, said nothing had been done to help lawyers defend detainees at the remote prison.
"We're being asked to go and defend these young people on our own dime. It's a way to prevent us from going to defend the innocent," she said.
"We expect the justice ministry to... put means at our disposal to allow us to go and defend our clients, and to guarantee our security," she added.