Rwanda's High Court on Thursday sentenced a former mayor to life in prison for his role in the country's 1994 genocide, which included leading attacks that resulted in the deaths of around 25 000 ethnic Tutsis in his town.

A statement from Rwanda's prosecution authority said the court "convicted him for genocide, extermination as crime against humanity and rape as crime against humanity and sentenced him to life imprisonment."

Ntaganzwa was however "not found guilty of murder as crime against humanity and direct and public incitement to commit genocide," the prosecution authority said.

Ntaganzwa - who had a $5-million US bounty on his head - was accused of organising "the massacre of thousands of Tutsis at various locations," the UN-backed Mechanism for International Criminal Tribunals (MICT) said when he was arrested.

Ntaganzwa is the third suspect to be tried in Rwanda, after earlier genocide accused were tried by the UN-backed International Criminal Tribunal for Rwanda (ICTR), based in Tanzania, which closed in 2015.