The U.N. war crimes tribunal for Rwanda on Friday acquitted two former ministers of genocide charges, making them among the most high-profile officials to be found not guilty of playing key roles in the 1994 slaughter of about 800,000 people.

The International Criminal Tribunal for Rwanda ordered the immediate release of former Health Minister Casimir Bizimungu and Jerome-Clement Bicamumpaka, who was foreign affairs minister at the time of the mass killings.

The Trial Chamber convicted two other former ministers, Justin Mugenzi and Prosper Mugiraneza, of conspiracy to commit genocide and public incitement to commit genocide.

Ethnic Hutu militia and soldiers butchered 800,000 minority Tutsis and politically moderate Hutus over 100 days between April and June 1994.

Mugenzi and Mugiraneza were convicted of conspiracy to commit genocide for their participation in the decision to remove Butare's Tutsi Prefect, Jean-Baptiste Habyalimana, the tribunal said in a statement.

Based on their participation in a joint criminal enterprise at the subsequent installation ceremony where President Théodore Sindikubwabo gave an inflammatory speech inciting the killing of Tutsis, the Trial Chamber convicted Mugenzi and Mugiraneza of direct and public incitement to commit genocide.

Sindikubwabo assumed the presidency in April 1994, after the incumbent Juvenal Habyarimana was killed when his plane was shot down outside the capital, Kigali. Habyarimana's death triggered the genocide.

Both were sentenced to 30 years in prison.

The court cut the sentences by 5 years because of undue delays in the trial.

Bizimungu was arrested in Kenya in February 1999 while Bicamumpaka was seized in April 1999, in Cameroon.