The move raised hopes the rebels might sign a peace settlement after 19 months of a brutal insurgency that displaced thousands of people in eastern Congo's North Kivu province.
M23 commander Gen. Sultani Makenga and his fighters were being held by the Ugandan military in Mgahinga, a forested area near the Congolese border. The rebels had been disarmed and were being registered by Ugandan officials, said the official, who spoke on condition of anonymity because he was not authorized to give this information.
"Makenga should be arrested and immediately brought before the courts," North Kivu Gov. Julien Paluku told The Associated Press. "He should be made to answer for his actions in eastern Congo."
The senior Ugandan official who spoke to The Associated Press about Makenga's surrender said the rebel leader and his fighters would be under Ugandan protection until regional governments, including those of Rwanda and Congo, agree on how to deal with "negative forces" in the region.
This week the M23 rebels lost control of all the territory they once held following an intensified offensive by Congolese troops who are backed by UN forces. After their last major stronghold fell last week, the rebels appeared to flee from the border town of Bunagana to the surrounding hills and forests. Earlier this week the rebels' civilian leader, Bertrand Bisimwa, announced the rebellion was over, saying he wanted to work with Congo's government toward finding a political solution to violence in eastern Congo.
A group of international envoys to Africa's Great Lakes region, including US envoy Russ Feingold, has been urging a political solution to the eastern Congo's crisis and urging both parties to reach a negotiated peace accord. Under the banner of a regional bloc, Uganda has been hosting peace talks between the rebels and Congo's government. Although those talks have repeatedly stalled since December, there were signs a final accord may now be signed after Congolese troops militarily defeated the rebels.
Feingold said Wednesday that an agreement between M23 and Congo's government "has been worked out in great detail" and could be signed by both parties within days. But the deal offers no amnesty for rebels who face serious criminal charges, he said.
"That is not happening in this case if this agreement goes through the way I believe it will go through, and certainly, the international community and the United States would not support such an agreement," Feingold said, talking about blanket amnesty for rebels. "I also believe that the Congolese government would never sign such an agreement this time."
M23 launched its rebellion in April 2012, becoming the latest reincarnation of a Tutsi rebel group dissatisfied with the Congolese government. M23 was created after officers from the Congolese army defected in April and May, demanding better pay, armaments and amnesty from war crimes. The rebels accused Congo's government of failing to honor all the terms of a peace deal signed in March 2009 with M23's precursor group, the CNDP.
A report by UN experts has said neighboring Rwanda, whose president is also Tutsi, provided weapons, recruits and training to M23 rebels. That report also said some in Uganda's military supported the rebels. Both Uganda and Rwanda deny the allegations.
M23 had been substantially weakened in the past year by internal divisions and waning Rwandan support. The Congolese military capitalized on these rebel setbacks by pushing ahead with new offensives beginning in August that were supported by a brigade of UN forces with a mandate to attack the rebels.