Former Congolese warlord Thomas Lubanga and militia chief Germain Katanga were on Saturday transferred to a prison in the Democratic Republic of Congo to serve out their sentences, the International Criminal Court said in a statement.
"This is the first time that the ICC designates a state to implement a sentence ordered by the court," said the ICC, which is based in The Hague.
Germain Katanga, 37, dubbed "Simba" the lion due to his ferocity, was sentenced to 12 years in prison last year by the ICC for his role in a brutal ethnic attack on a northeastern Congolese village in 2003.
In May 2014, the court found him guilty of complicity in crimes against humanity and war crimes over the February 2003 attack on the village of Bogoro, including murder and pillage.
Katanga was accused of supplying weapons to his militia in the attack in which some 200 people were shot and hacked to death with machetes.
Lubanga, another Congolese warlord and one-time adversary of Katanga, was jailed for 14 years in July 2012 for recruiting and enlisting child soldiers.
The court's presidency "underlined that Mr Lubanga and Mr Katanga have both expressed a preference to serve their respective prison terms in DRC, their country of origin," the ICC said in a statement.
The sentences' implementation will be subject to the court's supervision and "must conform to generally accepted international norms on the treatment of prisoners," it added.
Last month, the ICC cut the 12-year prison term imposed on Katanga after he voiced regret and for good behavior, and said he would now complete his sentence on January 18.
However Lubanga's request for early release was turned down by the ICC as "unjustified".
The Ituri region where the Bogoro massacre occurred has been riven by violence since 1999, when clashes broke out that killed at least 60,000 people, according to rights groups.
