Human rights organisation, Amnesty International, has asked Chad to ensure officers involved in the killings during the demonstrations in April and May are prosecuted.

Civil society groups and political parties held demonstrations calling for a return of constitutional order after the death of former President Idriss Déby Itno. The president's son, a four-star military general, has been in charge of the country.

The protests, which had been banned, were met with brutal force by security forces.

Hundreds of demonstrators were arrested and dozens died.

Amnesty International and other civil society organisations have in the past called for an investigation into the deaths.