25 July 2012 Last updated at 10:29 GMT
Rebel troops are under pressure in eastern Democratic Republic of Congo, following an offensive by UN-backed government forces, reports say.
The two sides have been involved in fierce fighting about 50 km (31 miles) north of the provincial capital, Goma.
The latest unrest began in April, with the UN and DR Congo government accusing neighbouring Rwanda of backing the rebels – a charge it denies.
More than 200,000 people in the region have been displaced by the conflict.
The BBC’s Gabriel Gatehouse in Goma says the fighting is centred around the Rutshuru area, about 50 km north of Goma.
This could mean government forces, supported by UN peacekeepers, have pushed the M23 rebels back, he says.
But this is a conflict without traditional front-lines, and fighting is taking place on multiple fronts, our reporter adds.
Civilians have been fleeing the area, seeking shelter in Goma or around nearby UN bases.
The rebellion is led by renegade general Bosco Ntaganda, who is accused by the UN of receiving military backing from Rwanda.
He belongs to the Tutsi ethnic group like the top leadership in Rwanda, which fears the presence of rival Hutu militas in eastern DR Congo.
Eastern DR Congo has been plagued by fighting since 1994, when more than a million ethnic Hutus crossed the border into DR Congo following the Rwandan genocide.
Rwanda has since twice invaded its much larger neighbour, saying it was trying to take action against Hutu rebels based in DR Congo.