The Congolese army has accused M23 rebels of killing about 50 civilians in the eastern town of Kishishe.
It comes amid reports of mass killings following the resumption of fighting, with a ceasefire agreed on last week appearing to be collapsing.
The rebel group has denied the allegations against them as “baseless”, saying it has never targeted civilians
Thousands of people are fleeing the fighting between the rebels, government forces and allied militias in different parts of North Kivu province.
Rwanda and the Democratic Republic of Congo agreed at talks in Angola that a ceasefire would take effect last Friday.
The M23 said the truce did not concern them as they were not invited to the talks. Rwanda denies allegations that it backs the M23.
Source: BBC Africa