Sultani Makenga, chief of Congo’s M23 rebels, held in Uganda

Uganda is holding the military commander of Congo's defeated M23 rebel movement after he surrendered, a Ugandan officer said on Thursday, allaying fears that it could still take up arms again.

Sultani Makenga's whereabouts had been unclear since Tuesday's declaration by the M23 that it was ending its 20-month-old insurgency in eastern Democratic Republic of Congo, worrying some that he could be hiding with plans to regroup.

His surrender will be seen as a major achievement for the Congolese army, with the backing of a U.N. force, as it strives to restore calm in a region wracked by war for two decades.

"I can confirm to you he is with us," the senior Ugandan officer, who asked not to be named, told Reuters when asked about Makenga's fate.

"He surrendered to us yesterday (Wednesday) and we're holding him somewhere and some other commanders of his," he said, adding the group of rebels would be held at an undisclosed location until a peace agreement was signed.

A Ugandan military official told the Associated Press that 1,700 M23 fighters were also in Uganda.

More from GlobalPost: M23 rebels in Congo: What a difference a year makes

Much will depend on the next move by Rwanda, which has been accused of supporting the rebellion since its start. The end of the M23's armed rebellion marks the first time in nearly two decades that there has not been a powerful militant group defending Rwanda's interests in eastern Congo.

Although Rwanda's government has strenuously denied supporting the M23, few outside the country believed them. United Nations investigators, human rights groups and journalists all gathered evidence to the contrary.

M23 was born out of a previous Rwandan proxy, the CNDP or National Congress for the Defense of the People, which was made up of mostly ethnic Tutsis. Former CNDP members accused the government in Kinshasa of backing out of a deal that was supposed to integrate the former rebels into the Congolese armed forces. They took the date of that deal, March 23, 2009, as the name for their new group.

It remains to be seen whether M23 will abide by its own promise to disarm, and how willing the Congolese government will be to hold political discussions after a rare and resounding military victory. 

Reuters and Agence France-Presse contributed to this report.