Ugandan military officials say at least 1,500 fighters from a rebel group in the neighboring Democratic Republic of Congo have surrendered, including the group's top commander.
The officials say Ugandan forces are holding M23 commander Sultani Makenga along with his fighters, after they turned themselves in.
Makenga is on both U.N. and U.S. sanctions lists. Human rights groups have accused rebels under his leadership of carrying out killings and sex attacks.
Earlier this week, M23 rebels declared they were giving up their fight against Congolese government forces after losing the last of the territory they once controlled in eastern Congo. The group vowed to pursue their goals through political means.
The rebels began surrendering their weapons on Wednesday.
A DRC army spokesman said Congolese forces now plan to go after other armed groups that operate on DRC territory, such as the Rwandan Hutu rebel group FDLR.
Eastern Congo has endured years of fighting involving the government and various rebel groups, usually over control of the area's rich mines.
M23 consists of fighters who joined the Congolese army in a 2009 peace deal but later defected after complaining of poor treatment. They launched their rebellion in April 2012 and seized territory in Congo's North Kivu province.
Congo has accused neighboring Rwanda and Uganda of supporting M23, an allegation both countries deny.