The Rwandan genocide ended after 100 days when Kagame's group seized control of the country [GALLO/GETTY]

A federal court in the state of Oklahoma has dismissed a lawsuit against Rwandan President Paul Kagame, brought by the widows of two assassinated African presidents, ruling that he had immunity in the US.

District Judge Lee West ruled on Friday that as a head of state recognised by the US government, Kagame was immune from the wrongful death civil suit. The Obama administration had urged the court to recognise Kagame's immunity.

Juvenal Habyarimana, then president of Rwanda, and Cyprien Ntaryamira, president of neighbouring Burundi, were killed in a rocket attack on their plane at Kigali airport in 1994.

The attack triggered the Rwandan genocide, in which Hutu armed groups and soldiers killed 800,000 minority Tutsis and moderate Hutus.

The widows had sought $350m in damages, arguing that Kagame, leader of the Tutsi rebel group, the Rwandan Patriotic Front, had ordered the assassination of their Hutu husbands.

The lawsuit was filed in Oklahoma in April 2010 during a visit by Kagame to speak at the graduation of 10 Rwandan students at Oklahoma Christian University.

The plaintiffs had argued the lawsuit against Kagame should go ahead, citing the US Supreme Court's 1997 ruling in Clinton v Jones that the sexual harassment suit against President Bill Clinton could proceed while he was still in office.

"We are pleased that we were able to win this matter on the long-standing doctrine of head of state immunity," said defence attorney Pierre-Richard Prosper, who served as a war crimes prosecutor for the UN International Criminal Tribunal for Rwanda from 1996 to 1998.

"We are confident, however, that had we been forced to address this matter on the merits we would have prevailed," Prosper said in a statement by his law firm, Arent Fox.

The Rwandan genocide ended after 100 days when Kagame's group seized control of the country.