Rebels in the Democratic Republic of Congo have seized the strategic town of Rutshuru in the east of the country.
Government forces reportedly retreated as the rebels advanced.
On Friday, 600 Congolese soldiers were reported to have fled into Uganda after M23 rebels seized the DRC side of the border town of Bunagana.
The rebels, loyal to renegade Gen Bosco Ntaganda, who is wanted for war crimes by the International Criminal Court, took up arms in April.
"We appeal to the international community to do something to protect the civilians who fled the fighting and are living in fear," Omar Kavota, a local official in Rutshuru, said to the Associated Press.
Rutshuru lies 70km (43 miles) to the north of the provincial capital Goma.
An Indian peacekeeper was killed as the rebels took control of the Democratic Republic of Congo side of the town of Bunagana on Friday, the UN said.
The rebels defected from the army after pressure increased on the government to arrest Gen Ntaganda, when one of his former colleagues was convicted of recruiting child soldiers by the ICC.
Some 200,000 people have fled their homes since April, with about 20,000 crossing the border to Uganda and Rwanda.
A recent UN report has accused Rwanda of backing the rebels - Gen Ntaganda is an ethnic Tutsi, like the majority of Rwanda's leadership.
But Rwanda has vehemently denied the accusations.
Mineral-rich eastern DR Congo has suffered years of fighting since 1994, when more than a million Rwandan ethnic Hutus fled crossed the border following the genocide, in which some 800,000 people, mostly Tutsis, were slaughtered.
Rwanda has twice invaded its much larger neighbour, saying it was trying to take action against Hutu rebels based in DR Congo. Uganda also sent troops into DR Congo during the 1997-2003 conflict.
The current mutiny is being led by fighters from Gen Ntaganda's former rebel group the CNDP, which was integrated into the Congolese national army in 2009 as part of a peace deal.
Known as "the Terminator", Gen Ntaganda has fought for various militias over the years but has told the BBC he has no involvement in the recent army mutiny.