A leader of Sudan's Janjaweed militia, which fought a war in the western Darfur region in early 2000, is in the custody of the International Criminal Court (ICC).
The ICC said Ali Kushayb surrendered voluntarily in the Central African Republic.
He is wanted on 50 counts of war crimes and crimes against humanity, including murder, rape and torture.
A warrant for his arrest was issued 13 years ago.
Sudan's former president Omar al-Bashir is also wanted by the court.
Some 300,000 people were killed and 2.5 million displaced by the conflict in Darfur.