Twenty civilians were killed early Wednesday in Ituri, in the Democratic Republic of Congo's volatile northeast, where the International Criminal Court says crimes against humanity could have taken place.
The pre-dawn attack took place in Djugu, north of Bunia, the capital of Ituri province, a local official told AFP.
"Given the insecurity that reigns over the zone, we are waiting for the return of a team on the ground to have an exact toll," the official said, speaking on condition of anonymity.
The official blamed the massacre on the Cooperative for the Development of Congo (CODECO) militia which is active in the region and blamed for several deaths.
CODECO is drawn from the Lendu ethnic group, a predominantly farming community who have historically clashed with the Hema, a group of traders and herders.
Hundreds of people have died in the North and South Kivu and Ituri provinces since last October, when the armed forces launched a crackdown on armed groups in the troubled east of the vast country.
Eastern Democratic Republic of Congo has been chronically unstable for a quarter of a century, its population terrorised by militias that are chiefly the legacy of two major wars.
UN rights chief Michelle Bachelet had spoken of "crimes against humanity" after visiting the northern region of Bunia in January, adding that the majority of victims were from the Hema group.
The International Criminal Court based in The Hague said the killings could constitute crimes under its purview.