Rwanda's highest court on Friday rejected an appeal by an opposition politician who was convicted for organizing an illegal gathering, inciting ethnic division and threatening state security.

Bernard Ntaganda, a former leader of Rwanda's PS-Imberakuri party, was not in court when the ruling was made to uphold his four-year jail sentence. He was arrested in July 2010 and convicted in February 2011.

Ntaganda, a Hutu, was accused of describing the government of President Paul Kagame as Tutsi-dominated and then calling for a power-sharing agreement between majority Hutus and minority Tutsis. He denied all the charges.

He is the third opposition leader to be charged under the country's stringent anti-genocide ideology laws that have been criticized by human rights watchdogs.

Victoire Umuhoza Ingabire, leader of FDU-Inkingi and a prominent Kagame critic, faces charges of genocide denial, threatening state security and inciting ethnic division. She announced earlier this month she would start boycotting court proceedings, saying the trial is politically motivated and cannot end in a fair decision.

Deogratius Mushayidi, leader of opposition group PDP Imanzi, is serving a life sentence for plotting to overthrow Kagame's government.

The cases against opposition politicians have highlighted Rwanda's struggle to move beyond the 1994 genocide, when extremist Hutus killed more than 500,000 Tutsis and moderate Hutus.

Human Rights Watch says the Rwandan government uses the genocide laws to stifle the opposition and muzzle the media.