Fulgence Kayishema was arrested after 22 years on the run
One of four remaining fugitives from the 1994 Rwandan genocide has been captured, UN prosecutors say.
Fulgence Kayishema was arrested in South Africa on Wednesday, they said. He is expected to face trial in Rwanda.
The former police inspector was charged in 2001 over an incident during which more than 2,000 Tutsi men, women and children were killed inside a Catholic church where they had sought refuge.
Some 800,000 Tutsis and moderate Hutus were killed in the genocide.
According to the indictment, Fulgence Kayishema directly participated in the planning and execution of a massacre of refugees hiding at the Nyange church in Kivumu, Kibuye prefecture, on 15 April 1994.
It says Mr Kayishema, born in 1961, and others tried to burn the church down with the refugees inside. When this failed, they bulldozed it, burying and killing all those hiding there.
Their corpses were then buried in mass graves.
In a statement, The Hague-based tribunal – known as the International Residual Mechanism for Criminal Tribunals (MICT) – hailed the international operation which had made it possible to apprehend Mr Kayishema.
South African police said an elite unit had arrested the suspect at a grape farm in Paarl, in Western Cape province. He had been living under the false name of Donatien Nibashumba.