Residents say that the Congolese army has taken control of a town that was run by M23 rebels for more than six months.
Jacques Kambale said early Saturday that lines of military entered the town of Kiwanja Friday afternoon.
Doctors Without Borders said late Friday that more than 55 civilians have been killed in fighting in another town in Congo's east, Kitchanga, where 135 people have been wounded. Thousands have fled the renewed violence.
Fighting began again in eastern Congo after the M23 divided into two groups on Wednesday. The new splinter group attacked positions held by M23 near the border with Uganda Thursday into Friday.
The M23 took Goma, the capital of North Kivu, in November but withdrew under international pressure. Congo's government promised negotiations with the group.