Rebel forces and pro-government militias in the Democratic Republic of Congo have been accused of war crimes by the United Nations.
Civilians are reported to have been killed in the eastern town of Kiwanja this week when it was captured by the rebel forces of Gen Laurent Nkunda.
However, the UN said investigators did not yet have a clear idea of what happened.
Fighting between government and rebels forces has left hundreds of thousands of people displaced since August.
Kiwanja is 80km north of the provincial capital Goma.
Human Rights Watch earlier claimed that civilians were killed in their homes in Kiwanja.
The BBC reports at least 26 people are known to have died. A UN military spokesman said that while some may have died in crossfire, others were summarily shot.
Over 5 million people have died in the Congo in the decade since 1998.
African leaders and UN Secretary-General Ban Ki-moon met in Nairobi on Friday to tackle the conflict, which is rooted in the 1994 genocide of some 800,000 Tutsis and Hutus in Rwanda.
UN forces weak
Kenyan Foreign Minister Moses Wetangula on Saturday lamented the weakness of UN peacekeepers in the conflict zone. The UN has a force of 17,000 in Congo.
At a press conference in Nairobi, Mr Wetangula asked: "What is the point of having 17,000 troops who cannot fire, who cannot disarm, who just walk around with blue helmets?"