Paul Kagame denies involvement in the 1994 crash that sparked the genocide
Rwandan President Paul Kagame has travelled to the US, ignoring a lawsuit filed there over the deaths of two African presidents in 1994.
Mr Kagame spoke at a ceremony honouring Rwandan graduates in Oklahoma City.
The widows of the then leaders of Burundi and Rwanda, whose deaths sparked the 1994 genocide, say Mr Kagame ordered their plane shot down.
Mr Kagame denies this. The lawyers who filed the lawsuit were unable to serve the legal papers during his visit.
Mr Kagame was keynote speaker at the Oklahoma Christian University ceremony on Friday.
He shook hands with the Rwandan students and other graduates, saying education would be crucial in helping his country continue to recover from genocide.
However he left before the event ended, making no public comment on the lawsuit. Witnesses said he was surrounded by security guards.
The widows of ex-Presidents Juvenal Habyarimana of Rwanda and Cyprien Ntaryamira of Burundi do not live in the US, but filed the wrongful death lawsuit in Oklahoma City because of Mr Kagame's ties to the university, their attorneys said. They are seeking $350m in compensation.
A university spokesman told the Associated Press news agency that Mr Kagame had come to honour the students "and we're not going to get involved in the politics of the country".
In 1994 Mr Kagame was the rebel leader heading the Rwandan Patriotic Front (RPF), which ousted the genocidal regime.
The plane carrying President Habyarimana - a Hutu - and Mr Ntaryamira was shot down on 6 April 1994. The Hutu extremist government accused the RPF of being responsible.
Within hours, militias set up roadblocks and started to murder Tutsis and moderate Hutus systematically. Some 800,000 people were killed over the next 100 days.
The RPF has always accused Hutu extremists of shooting down the plane, to provide a pretext for carrying out their genocidal plans.
Allegations in France
Mr Kagame has also faced French allegations of involvement in the crash.
Earlier this week, French media reported that a Paris judge investigating the crash, Marc Trevidic, was planning to send experts to Rwanda.
Mr Trevidic's predecessor, Jean-Louis Bruguiere, had accused the RPF of shooting down the plane and called for the arrest of President Kagame.
The move led Rwanda to break off diplomatic relations with France. The Kigali government also accused France of supporting the deposed extremist Hutu regime.
However a visit by French President Nicolas Sarkozy in February was widely seen as a sign a rapprochement between the two countries. Mr Sarkozy acknowledged France had made "mistakes" during the 1994 genocide.