Growing tensions in the east of the Democratic Republic of Congo threaten to re-ignite widespread fighting, Amnesty International has warned.
The human rights organisation says rival factions are inflaming ethnic divisions in North Kivu province to promote their own interests.
It accuses Uganda and Rwanda, which previously invaded eastern Congo, of having a "detrimental effect".
It urges UN peacekeepers in eastern DR Congo to do more to protect civilians.
"North-Kivu is currently the stage on which national and regional political and military antagonisms are being played out - and the end result is looking increasingly tragic for the people of the region," said Kolawole Olaniyan, director of Amnesty International's Africa programme.
Amnesty's report, titled North-Kivu: Civilians pay the price for political and military rivalry, says former parties to the war seem reluctant to dismantle their military structures and to participate in a united national army.
"However, real unification of the armed forces is a prerequisite for elections that are free of human rights abuses, and for the success of future peace-building in the country," Mr Olaniyan said.
Amnesty International said no effort had been made to exclude from the unified army individuals suspected of committing grave human rights abuses, and to bring them to justice.
The human rights organisation emphasised the need for the international community, particularly the 19,000-strong UN Mission in the Congo (Monuc), to play a more active role.
"Despite the clarity of its protection mandate in the Kivu provinces, Monuc has failed on several occasions to protect civilians, often intervening too late to prevent human rights abuses.
"Monuc must reinforce its presence in regions at risk of escalation of violence, including North-Kivu, and ensure that it acts promptly to protect civilians," Mr Olaniyan said.