Congolese fighter planes have bombed M23 rebel positions in the east of the country, causing people to flee into neighbouring Uganda, local media reported.
A rebel spokesman said the jets deliberately targeted civilian settlements around the Sabyinyo volcano.
The military denied the accusation.
Kinshasa accuses Kigali of supporting the M23 rebels, which Rwanda has constantly denied.
Aid groups say tens of thousands of people have fled to camps near the regional capital Goma following the upsurge in fighting.