At least two dozen people, most of them women, have been killed over the past week in ethnic violence between Bantus and Pygmies in southeastern Democratic Republic of Congo, a U.N. human rights official said on Monday.

The Luba, a Bantu ethnic group, and the Twa, a Pygmy people who inhabit Central Africa’s Great Lakes region, have been in conflict since May 2013 in Congo’s Katanga region, known for its rich deposits of copper and other metals. 

Clashes have been fuelled by social tensions between Bantu villagers and the Twa, a hunting and gathering people who have long been denied access to land and basic services. Attacks by militiamen from both groups have left hundreds dead.

José Maria Aranaz, head of the United Nations Joint Human Rights Office (UNJHRO), said that at least 24 people, including 19 women, have been killed in Moba, a town located on the shores of Lake Tanganyika, since Jan. 11.

“A particularly worrying pattern we have documented is the way in which women have been targeted, both generally in the violence but also with sexual violence,” Aranaz told Reuters.

The UNJHRO has documented at least 158 deaths, 205 injuries and 50 rapes resulting from the ethnic violence since last July.

Nearly 200,000 people were forced to flee clashes during the same period, said Yvon Endoumou, spokesman for the U.N. Office for the Coordination of Humanitarian Affairs.