Instigated by the Hutu extremist regime in Rwanda at the time, the United Nations estimates that around 800,000 people, mostly from the Tutsi minority, were killed over 100 days in an ethnic pogrom.
HRW said in a statement that "a significant number of individuals responsible for the genocide, including former high-level government officials and other key figures behind the massacres, have since been brought to justice."
But the rights group added that "in recent years, several high-level alleged genocide masterminds have died, or, in the case of one alleged planner, been declared unfit to stand trial, highlighting the urgent need to continue the quest to deliver justice."
In June, a U.N. court in The Hague declared that a presumed funder of the genocide now in his 80s could not be tried because of his deteriorated mental state.
International prosecutors determined in November that Aloys Ndimbati, one of the last remaining fugitives suspected of playing a major role in the killings, had in fact died in Rwanda in 1997.
Two senior genocide suspects are still on the run.
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