Elizaphan Ntakirutimana, 73, who was sought by a United Nations tribunal on charges of genocide and crimes against humanity, had been under FBI surveillance for months in this dusty border town, where he has relatives.
But authorities did not authorize an arrest until Thursday, when he attempted to leave.
Ntakirutimana, the pastor of a Seventh-day Adventist Church, was accused of participating in Rwanda's 1994 state-sponsored massacre of mostly minority Tutsis. More than 500,000 people died in the bloodshed, which ended only after Tutsi forces seized control of Hutu-led government.
The tribunal alleges that Ntakirutimana arranged for hundreds of Tutsis in Rwanda's Kibuye district to seek refuge at his church.
Then, after throngs of men, women and children crowded in for safety, Ntakirutimana arrived with a truckload of armed men and directed them to start killing, the tribunal contends.
Hundreds were killed and many wounded. In the months following the massacre, Ntakirutimana helped track down and execute additional Tutsis, including those who survived the church slaughter, according to the tribunal.
Assistant U.S. Attorney Don DeGabrielle said two indictments against Ntakirutimana remain sealed. He would not disclose exactly how many people died in the massacre.
Ntakirutimana made an initial court appearance Friday before a federal magistrate, who ordered him held without bond pending a detention hearing next week.
DeGabrielle said he would seek Ntakirutimana's extradition to Tanzania, where the U.N. International Criminal Tribunal for Rwanda is assembled. Though the tribunal has indicted 21 people, most have not been captured.
=A9 Copyright 1996 The Associated Press