At least eight people have been killed in the first clashes between rival factions of the M23 rebel group in DR Congo.
The violence was linked to a power-struggle between M23 political leader Jean-Marie Runiga and military chief Sultani Makenga.
On Sunday, regional leaders signed a UN-brokered accord to end conflict in eastern Democratic Republic of Congo.
About 80,000 people have been displaced in fighting since May 2012.
The M23 launched a rebellion against the DR Congo government, briefly seizing Goma, the main city in the east, in November.
Both Rwanda and Uganda strongly deny claims they back the rebels. The rival M23 factions exchanged gunfire in the town of Rutshuru, 70km north of Goma. Congolese sources told him eight people had been killed - including six civilians.
But one source said that 19 people were killed - nine civilians and six fighters, including two majors.
The M23 denied that it was hit by dissent, our reporter says.
It blamed the violence on the FDLR rebel group, which is made up of Rwandans accused of involvement in the 1994 genocide that left about 800,000 people dead, he says.
The M23 is involved in separate peace talks with the DR Congo government in Uganda. In January, it declared a unilateral ceasefire. The talks could run into trouble if the M23 mediation team splits between
supporters of Mr Runiga and Col Makenga.