ADDIS ABABA, Ethiopia (AP) — Rebels in South Sudan are forcibly recruiting civilians to march on the capital, the military said, even as representatives of the warring factions gathered in neighboring Ethiopia on Thursday for the start of peace talks. The fighting underscored the challenge facing African mediators as they try to nudge two rivals —President Salva Kiir and ousted Vice President Riek Machar —toward the negotiating table after more than two weeks of bloody violence in the world’s newest country. South Sudan has been plagued by ethnic tension and a power struggle within the ruling party that escalated after Kiir dismissed Machar as his vice president in July, with the violence boiling over in mid-December. The rebels back Machar, who is now a fugitive sought by the military. Rebels currently hold Bor, the capital of the key oil-producing state of Jonglei that is seeing some of the fiercest fighting of the conflict. Military spokesman Col. Philip Aguer said the central government had sent in reinforcements from Juba, the capital. He said rebels were arming reluctant civilians as they focus on their next target: Juba. ‘‘Juba, that is their intention,’’ he said. ‘‘They are trying to march to Juba. The (South Sudanese military) will return them to where they came from.’’ It was not possible to independently verify Aguer’s account. The fighting has overshadowed efforts in neighboring Ethiopia, which is playing a leading role in trying to extract a cease-fire deal from both sides. In Addis Ababa, the Ethiopian capital, African mediators under the banner of a regional bloc met representatives for both sides, briefing them separately ahead of the official start of direct talks. Face-to-face meetings between the two groups were not expected to start until later in the week. One delegate from Machar’s side said he believed the first direct meetings would happen on Saturday. The United Nations and the African Union have said they support the efforts by East African leaders to broker peace in South Sudan. Kiir on Wednesday declared a state of emergency in the states of Jonglei and Unity, where rebels also control the capital. The fighting has exposed ethnic rivalry between the country’s two largest ethnic groups, the Dinka of Kiir and the Nuer of Machar. The U.N. says there is mounting evidence that people were targeted for their ethnicity. More than 1,000 people have been killed and nearly 200,000 displaced by violence. Kiir insists the fighting was sparked by a coup attempt mounted by soldiers loyal to Machar on Dec. 15 in Juba. But that account has been disputed by some officials of the ruling party, who say the violence began when presidential guards tried to disarm their Nuer colleagues. From there, violence spread across the country, with forces loyal to Machar defecting and seizing territory from loyalist forces. South Sudan’s government said in Twitter updates Thursday that the military had formed committees to ‘‘investigate those involved in killing people,’’ as well as the fight among presidential guards. It also said ‘‘criminals’’ accused of looting from civilians had been arrested. Machar has criticized Kiir as a dictator and says he will contest the 2015 presidential election. South Sudan peacefully broke away from Sudan in 2011 following a 2005 peace deal. Before that, the south fought decades of war with Sudan. In New York, U.N. humanitarian chief Valerie Amos said that some 194,000 South Sudanese have been driven from their homes by the violence, and more than 57,000 are under protection at U.N. peacekeeping bases. She said the United Nations has provided 107,000 with U.N. assistance, and the world body aims to reach over 600,000 South Sudanese with humanitarian aid in the next three months. ___ Associated Press writer Peter James Spielmann at the United Nations contributed to this report.