KIGALI, Rwanda — A Rwandan court sentenced the country’s top opposition political leader to eight years in prison on Tuesday for treason and a charge stemming from this central African nation’s murderous ethnic attacks 18 years ago: genocide denial.

The opposition leader, Victoire Ingabire, returned to Rwanda in 2010 after living abroad for 16 years and quickly visited the country’s genocide memorial, where she asked why Hutus killed in the violence were not recognized like the minority Tutsis were. She had planned to run for president but instead was arrested.