UN investigators in the Democratic Republic of Congo say they have found mass graves with about 30 bodies in an army camp in the east of the country.
The dead included women and children who appeared to have been murdered, a UN spokesman said. He believed they had disappeared in the last few months.
The authorities have arrested two soldiers in connection with the finding in the town of Bavi in Ituri district.
The army has been deployed in the area to stop fighting between local militia.
The discovery comes amid continued uncertainty in the capital Kinshasa following the re-election of incumbent leader Joseph Kabila in presidential elections.
The finds followed a tip-off from a military witness, military prosecutor John Penza said.
He said two army officers had been arrested in connection with the discovery.
"There are bodies of men, of women, of children, some still not decomposed. It is horrible," he added.
A UN spokesman said witnesses had accused the Congolese army of involvement.
"There are witnesses who directly accuse the First Brigade, which is based there (in Ituri), of being responsible," Kemal Saiki said.
Correspondents say the First Brigade is one of several Congolese army brigades made up of fighters from factions who fought in Congo's 1998 - 2003 war.
Violence continues in the east and north of the country, despite the presence of thousands of UN peacekeeping troops.
Ituri, on the Ugandan border, is one of the most volatile regions because of intense rebel activity.
The Lendu and Hema ethnic groups are at war in the area, where Uganda's influence is strong.