Hissene Habre, the former ruler of Chad, has been arrested in Senegal ahead of his trial there over alleged political killngs and torture during his time in power.
Habre has been living in exile in Senegal for the last 22 years.
Habre, who led Chad between 1982 and 1990, will be tried in a special court set up this year by Senegalese authorities in agreement with the African Union.
The case against Habre follows years of procrastinating by Senegal under former president Abdoulaye Wade. It will be first time the former leader of an African state has been tried by another.
"He was arrested this morning and placed in police custody after a request by the prosecutor," said Marcel Mendy, the court's spokesman on Sunday.
Mendy did not give any further details on the arrest. Habre is not actually expected to appear at the court before early 2015 as investigations by the court's prosecutors are ongoing.
Local media published photos of Habre, in traditional white flowing robes, being led away by security forces from his mansion in the capital, Dakar.
Habre's lawyers called the arrest a "kidnapping" and demanded his immediate release.
But rights groups welcomed the move.
"The wheels of justice are turning", said Reed Brody, counsel for Human Rights Watch who has worked with Habre's victims since 1999. "After 22 years, Habre's victims can finally see the light at the end of the tunnel."
Visiting Senegal on Thursday, US President Barack Obama highlighted Senegal as an example in Africa for the independence of its judiciary.