The High Court in Kigali this week found Victoire Ingabire, leader of the opposition FDU-Inkingi party, guilty of ties to terrorism and for inciting anti-government action. Some of the charges were issued for her alleged downplaying of the Rwandan genocide in 1994.
Ingabire, a Hutu, was sentenced to eight years in prison for what Human Rights Watch said was a sign of the government's intolerance of dissent.
"The prosecution of Ingabire ... illustrates the Rwandan government's unwillingness to tolerate criticism and to accept the role of opposition parties in a democratic society," Daniel Bekele, Africa director at Human Rights Watch, said in a statement from Kenya. "The courts should not be used for such political purposes."
The rights group said it can't comment on the "veracity of the charges" tied to Ingabire's ties to armed groups but expressed concern that evidence used against her was unreliable.
Conflict between the Hutu and Tutsi ethnic communities left roughly 800,000 people dead in a 100-day massacre in 1994.
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