The UN mission in the Democratic Republic of Congo has accused Gen Laurent Nkunda's rebel forces and pro-government militias of war crimes, BBC reports.
The alleged crimes took place in the eastern town of Kiwanja this week when it was captured by Gen Nkunda's forces. Several civilians were reported killed.
But 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.