A group of 25 men appeared before a military tribunal in Kigali as suspected operatives for the rebel group, Rwanda National Congress (RNC), which the government labelled as a terror organisation.
The RNC is mainly composed of former allies of President Paul Kagame, now bitter foes, residing mainly in exile.
It was started in 2010 by Kayumba Nyamwasa, the former chief of staff of Rwanda Defence Forces and the late Patrick Karegeya, Rwanda's former Chief of Intelligence--whose murder in Johannesburg December 2013 caused a cessation in relations between South Africa and Rwanda.
The men who appeared in court on Wednesday include three who identified themselves in court as Burundian citizens, two said are Ugandan and one identified as a Malawian.
They were all charged with four crimes, including; committing acts to harm the established government or attempting to overthrow the government by use of military force, maintaining relations with a foreign government with intent to wage a war, formation and joining a criminal association, as well as joining an illegal armed group.
The charges attract between 25 years in prison and life imprisonment.
It is not yet known when or how they were arrested or for how long they have been in custody. The pre-trial is still ongoing.