General Leon Mushale told reporters yesterday in the eastern city of Goma that a further 25 rebels either were captured or surrendered and that six soldiers had been injured.
The clashes occurred in the eastern part of DR Congo, on and near the border with Uganda, on January 31 and also on February 20 to 22, according to the army.
Mushale, who heads military operations in North Kivu province, said the rebels fled "some to Uganda, others to Rwanda".
The militia was defeated the following year, and hundreds of fighters fled the country.
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But in January, the Congolese government and numerous witnesses said former M23 rebels were spotted in the North Kivu village of Rutshuru, having crossed over from neighbouring Uganda.
The group still poses a threat to peace and security in the east of DRC, said UN peacekeeping mission MONUSCO, adding it has received "many signs" that former fighters remain.