KHARTOUM, Sudan — The government of South Sudan refused Saturday to release all 11 senior politicians who were detained on allegations of plotting a coup as a condition for a truce with rebel forces.
“It is not accepted,” Michael Makuei Lueth, South Sudan’s information minister, said in a phone interview. “That is a condition, and we said we will enter negotiations with no preconditions.”
The 11 were arrested two weeks ago after President Salva Kiir said they had joined the former South Sudanese vice president, Riek Machar, in plotting to overthrow the government.
The arrests inflamed violence across the country, which is now believed to have killed thousands of people. Machar, who denied orchestrating any coup attempt, fled the capital, Juba, and his whereabouts have not been disclosed.
Meanwhile, 25,000 young men who make up a tribal militia known as the ‘‘White Army’’ are marching toward a contested state capital in South Sudan, an official said Saturday, dimming hopes for a cease-fire.
On Friday, East African leaders trying to end the crisis announced that they had made progress on a peace deal. The South Sudanese government said it would release eight of the prisoners, and later freed two of them: Deng Deng Akon, the former executive director for Machar’s office, and Peter Adwok, the former higher education minister.
Machar remained skeptical about the proposed cease-fire, and told the BBC, “All the detainees must be released before we talk substantial issues.”
But Ateny Wek Ateny, the presidential spokesman, said Saturday that the government had no plans to release three of those detained and would continue investigating the other eight men to see if they had been part of a coup attempt.
The three it refuses to release are Kosti Manibe, the former finance minister; Deng Alor, the former cabinet affairs minister; and Pagan Amum, the former secretary general of the governing party, the Sudan People’s Liberation Movement. All three are senior members of the party.
“They are being held on charges of corruption,” Ateny said in an interview.
What began as a political struggle in the party soon took on an ethnic dimension as fighting broke out between the two largest ethnic groups in South Sudan, the Dinka and the Nuer. Kiir is a Dinka, and Machar a Nuer.
The conflict has set off a humanitarian crisis, with tens of thousands seeking refuge at UN compounds throughout the country. The United Nations has called for $166 million in humanitarian aid.
There is a looming battle for Bor, the provincial capital of Jonglei state that briefly fell to rebels before government forces took it back this week, said military spokesman Colonel Philip Aguer. Pro-Machar forces are believed to be preparing a fresh offensive to retake Bor.
Bor is the town where three United States military aircraft were hit by gunfire while trying to evacuate American citizens on Dec. 21, wounding four US service members.
An estimated 25,000 youths from the Lou Nuer sub-clan — the same tribe Machar is from — are marching on Bor, Lueth said. The ‘‘White Army’’ gets its name in part from the white ash fighters put on their skin as a form of protection from insects.
The White Army has threatened the central government in recent past.
In 2011 the army said that the Nuer youths would fight until all the Murle — another tribe — had been killed. The statement warned the national military to stay out of the way. Another statement warned that the White Army would ‘‘wipe out’’ the army, according to the Enough Project, a US-based advocacy group that works on issues in central Africa.