A Belgian Catholic priest has been arrested at the airport in Rwanda's capital, Kigali, for his alleged role in the 1994 genocide.
Guy Theunis worked as a missionary in Rwanda, a former Belgian colony, from 1970 until 1994.
Belgium's Foreign Minister Karel de Gucht has expressed his "astonishment".
Several Rwandan priests and nuns have been convicted of participating in the killing of some 800,000 minority Tutsis and moderate Hutus.
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Rwandan prosecutor Emmanuel Rukangira told the BBC that Father Theunis had incited Rwandans to commit genocide by republishing articles from extremist publication Kangura in his Dialogue magazine.
Former Kangura editor Hassan Ngeze has been sentenced to life in prison by the United Nations court set up to try those responsible for the genocide.
Mr Rukangira said Father Theunis would be tried by the Gacaca village courts set up to deal with genocide suspects.
He was in transit through Rwanda from Democratic Republic of Congo when he was arrested.
Mr de Gucht said he had asked for an explanation from Rwanda.
Some members of the Catholic hierarchy in Rwanda had close ties to extremist politicians and aided Hutu militias in the run-up to the 1994 killings.
Thousands of Tutsis were slaughtered after seeking sanctuary in churches.
In 2001, a Brussels court convicted two Rwandan Catholic nuns for their roles in the genocide.
In the 11 years since the genocide, some Rwandans have converted to Islam, saying the churches let them down.