NAIROBI, Kenya -- The United Nations has discovered a mass grave in South Sudan containing about 34 bodies, the world body said Tuesday, amid a wave of ethnic killings in the world's newest country over the last 10 days.
The U.N. said it received reports of 41 additional people "unaccounted for and feared dead."
Word of the mass grave came as South Sudan undertook military operations to wrest back control of the city of Bor from rebels loyal to the country's former vice president. One potential complicating factor: The military said armed elements have entered a U.N. refugee camp in Bor that holds about 17,000 civilians.
The mass grave was found in Bentiu, U.N. human rights chief Navi Pillay said. At least two other mass graves are reported to have been found in Juba, she said in a statement Tuesday.
The bodies in Bentiu reportedly belonged to the ethnic Dinka, who were members of the Sudan People's Liberation Army, said Ravina Shamdasani, a spokeswoman for the Geneva-based human rights office.
Responding to the discovery, the government minister of information Michael Makuei Lueth said: "Of course Bentiu is under the control of the rebel leader Riek Machar, so we have nothing to do with that area."
The United States and Ethiopia are leading efforts to open peace talks on the crisis. Officials say President Salva Kiir and former Vice President Riek Machar have agreed to meet but specifics including the status of Machar's imprisoned compatriots are holding up talks.
South Sudanese troops are advancing on Bor in order to take it back from troops loyal to Machar, said military spokesman Col. Philip Aguer. Troops will also soon advance on another rebel-held city, Bentiu, in the oil-rich region of Unity state, he said.
"We have already started in Bor," Lueth said.
The U.N. has staff in the country investigating the incidents of mass killings, said Pillay. It is unclear who is responsible for the killings, she said. The other two reported mass graves are in Jebel-Kujur and Newside, near Eden, she said.
The top U.N. humanitarian official in the country said Monday that he believes the death toll from 10 days of violence has surpassed 1,000 but that there are no firm counts. The official, Toby Lanzer, estimated that there are more than 100,000 internal refugees across the country seeking shelter from the violence.