Ethiopian Prime Minister Hailemariam Desalegn, middle, South Sudanese President Salva Kiir, right, and Kenyan President Uhuru Kenyatta before their meeting at State House in Juba, South Sudan on Thursday. — AP JUBA — Fighting persisted in parts of South Sudan's oil-producing region as African leaders on Thursday tried to mediate between the country's president and the political rivals he accuses of attempting a coup that the government insists sparked violence threatening to destroy the world's newest country. Kenyan President Uhuru Kenyatta and Ethiopian Prime Minister Hailemariam Desalegn met with South Sudanese President Salva Kiir on Thursday. A senior government official warned that Riek Machar, the former vice president who now allegedly commands renegade forces in the states of Unity and Upper Nile, had to renounce rebellion before the government could negotiate with him. Michael Makuei Leuth, South Sudan's information minister, said the government has not yet established formal contact with Machar. “For us, we are not talking with him,” Leuth said, referring to Machar, whose whereabouts remain unknown. It was not possible to reach Machar, as his known phone numbers were switched off. Government troops are trying to retake control of Bentiu, the capital of oil-rich Unity state, from forces loyal to Machar. There was also reported fighting in Malakal, the capital of Upper Nile state, according to Lueth. Upper Nile and Unity comprise the country's key oil-producing region, raising fears unrest there could cut off the country's economic lifeblood. World leaders have urged the country's leaders to stop the violence in which thousands are feared killed. The United States, Norway and Ethiopia are leading efforts to open peace talks between Kiir and his political rivals. Kiir said in a Christmas address that he is willing to “dialogue” with all his opponents. The United Nations is investigating reports of mass killings since violence began spreading across South Sudan after a fight among the presidential guards on Dec. 15, pitting soldiers from Kiir's Dinka ethnic group against those from the Nuer ethnic group of Machar. South Sudan's top U.N. humanitarian official, Toby Lanzer, said on Monday that he believes the death toll has surpassed 1,000. South Sudan gets nearly 99 percent of its government budget from oil revenues. “We are moving toward them and we will flush them out like we did in Bor,“Leuth said, referring to the capital of Jonglei state that government troops retook from renegade forces earlier in the week. Although the capital, Juba, is now calm, fighting appears to be spreading across the country, stretching the limits of humanitarian workers and aid agencies. The UN humanitarian office said aid agencies need $166 million to save lives amid continuing violence. “The resources will be used to provide clean water and sanitation, health care, shelter, and deliver food and livelihood assistance,” the office said in a statement. “It will also ensure that the rights of vulnerable people, including survivors of violence, are better protected. The money will be used to manage sites for displaced people and transport aid workers and supplies to strategic locations where communities are most at risk.” Some 58,000 people have taken refuge in and around UN bases in the country and more than 92,000 have fled their homes as a result of fighting that has raised fears of a civil war in the country, according to the United Nations. — AP