Fighting between the rebels and soldiers flared up on Wednesday after several days of calm following earlier clashes that led to tens of thousands of people to flee the region.
Rebels from the M23 group have captured several villages in eastern DR Congo following clashes with government troops in the Rutshuru region, local sources have said.
There were fierce clashes around the Virunga National Park on Saturday, a UNESCO-listed world heritage site home to endangered mountain gorillas, said one source in the reserve.
The front line was at Matebe, Rutshuru, North Kivu province, the source added.
"The M23 rebels occupy Gisiza, Gasiza, Bugusa, Bikende-Bugusa, Kinyamahura, Rwambeho, Tshengerero, Rubavu and Basare" and still held Runyoni and Tchanzu, said Nestor Bazirake, the spokesman for a group of villages in nearby Jomba.
Government troops held Bunagana and the Rwanguba bridge, he told AFP, but locals had already fled across the border to Uganda or to neighbouring regions inside DR Congo.
AFP was unable to get a statement from either military sources or regional officials.
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Fighting between the rebels and soldiers flared up on Wednesday after several days of calm. The earlier clashes had already led tens of thousands of people to flee the region.
The M23 was born among former members of a Congolese Tutsi militia that was once supported by Rwanda and Uganda.
The rebels had been incorporated into the Congolese army under a peace deal signed on March 23, 2009.
In 2012, they mutinied, saying the deal had not been upheld and named their group the March 23 (M23) Movement.
Becoming one of the scores of armed groups that roam eastern DR Congo, M23 briefly seized the city of Goma before being defeated and forced out of the country.
After its defeat, the M23 eventually signed an accord with Kinshasa that included provisions for its rebels to reintegrate into civilian society.
But the group has again accused the government of reneging on the deal and resumed fighting last year.
Their latest offensive began in late March.
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