A special court on Friday accused the former leader of a key militia in the Central African Republic of crimes against humanity at the height of the civil war.
Former captain Eugene Barret Ngaikosset, arrested nearly a week ago, was once a commander of the guard of president Francois Bozize, who was toppled in 2013 by the Seleka, a coalition of largely Muslim armed groups.
He then became an important leader of the largely Christian and animist anti-Balaka militias, which Bozize founded to fight the Seleka.
The two groups plunged the country into a bloody civil war, with the United Nations accusing them in 2015 of having committed war crimes and crimes against humanity between 2014 and 2015.
Ngaikosset, arrested September 4 just outside the capital Bangui, "was accused of crimes against humanity" by two judges of the Special Criminal Court (CPS), the tribunal said in a statement.
Made up of Central African and international magistrates, the court has been tasked with judging serious human rights violations since 2003 in this country that has been locked in civil war since 2013.
CPS prosecutors must decide if Ngaikosset will be placed in custody while awaiting a possible trial, the statement said.
The International Criminal Court in The Hague could also be tasked with handling the former captain's case.
Ngaikosset is dubbed by Central African media as "the butcher of Paoua," referring to massacres committed by the army in the northwest city of the same name from 2005 to 2007, when he was a commander of Bozize's dreaded presidential guard.
In a 2009 report, Human Rights Watch (HRW) said diplomats had at the time asked Bozize to take legal action Ngaikosset, who it said was implicated in generalised atrocities in the northwest.
The ex-captain had set up a faction of the anti-Balaka, which means anti-machete, after Bozize's fall in 2013.
And a report from the UN, which froze his assets abroad and issued a travel ban, accused him in 2015 of carrying out or supporting actions contrary to international human rights law.
The civil war has dropped in intensity since 2018 but armed groups, some with past links to the Seleka or anti-Balaka, occupied late last year more than two-thirds of the country.
Late last year, some elements launched a rebellion against the administration of President Touadera, who was re-elected on December 27.
His army, with the support of hundreds of Russian paramilitaries and Rwandan soldiers, have today largely reconquered lost territory.