KAMPALA (Reuters) - Police in Uganda have arrested one of the most wanted suspects from Rwandas 1994 genocide, Idelphonse Nizeyimana, a senior police source said Tuesday. Nizeyimana, a former army captain and senior intelligence officer, had entered Uganda from Democratic Republic of Congo on October 1 and was detained in Kampala Monday, the source said. He had been extradited to Arusha, northern Tanzania, to the International Criminal Tribunal for Rwanda (ICTR), he said. ICTR officials did not immediately confirm the news. Nizeyimana was among the dozen most wanted suspects sought by the UN court over the genocide in which about 800,000 ethnic Tutsis and politically moderate Hutus were killed. The US had offered a $5 million reward for his capture. He is charged by the ICTR with genocide, complicity in genocide, and direct and public incitement to commit genocide. The tribunal says Nizeyimana and others prepared lists of Tutsi intellectuals and those in authority before handing the lists to troops and militia who then killed them. He is also accused of setting up roadblocks where Tutsis were slaughtered, and of providing weapons and transport to militia in the knowledge they were being used for attacks. Rwandas government, which says Nizeyimana was the main organizer of the genocide in the southern province of Butare, says he has spent the 15 years since the slaughter fighting for a Hutu rebel group in the forests of neighbouring eastern Congo.