The Ugandan president said on Monday (30.12.2013), East African nations had agreed to defeat Riek Machar's rebels, should he reject a ceasefire offer. "We gave Riek Machar four days to respond and if he doesn't we shall have to go for him, all of us. That is what we agreed in Nairobi," Museveni told reporters in South Sudan's capital, Juba.

Regional leaders from the Intergovernmental Authority on Development (IGAD), an eight-country trading bloc based in Eastern Africa, had given Machar and Kiir up to December 31 to lay down their arms and start peace talks. Ethiopian Foreign Minister Tedros Adhanom and Ugandan President Yoweri Museveni visited Juba ahead of the deadline to ramp up the pressure on the warring factions.

Agina Ojwang, an analyst on East African affairs, told DW Museveni's decision to intervene militarily showed he could not be trusted to bring the conflict to a peaceful settlement. "Museveni is contemplating a situation where he will move more of his forces into southern Sudan, he is also trying to arm twist other IGAD members to side with him," Ojwang noted.

In Jonglei, reports of an imminent attack by a South Sudanese militia known as the "White Army," forced hundreds of residents to flee the capital Bor, officials said on Monday.

More than 1,000 people have been killed since fighting broke out in the capital, Juba in mid-December. Since then, the clashes between supporters of two political rivals, have taken on an ethnic dimension pitting President Salva Kiir's Dinka tribe against former Vice President Riek Machar's Nuer ethnic group. "The forces of Riek Machar are now advancing on Bor, but we are confident we will hold them off and protect the town," army spokesman Philip Aguer said.

Return of the White Army

The White Army comprising mostly Nuer youths got its name from the ash prepared from burnt cow dung, with which they cover themselves to ward off insects. The militia has in the past sided with Riek Machar, whom President Kiir accuses of plotting to overthrow his government.

However, a spokesman for the government of South Sudan's Unity State, which is controlled by forces loyal to Machar, denied the former sacked vice president was commanding the White Army fighters. His remarks have raised fears that the violence was spreading beyond the control of widely-recognized ethnic leaders. Nuer militias are believed to have massacred Dinkas in Bor during ethnic clashes in 1991.

Bor's mayor, Nhial Majak Nhial, said he was urging civilians to leave Bor, as the White Army militia nears. The spokesman for the South Sudan's Army (SPLA), Phillip Aguer said a small SPLA reconnaissance unit had clashed with the White Army militia on Sunday (29.12.2013). Tribal elders over the weekend persuaded many of the Nuer youths to abandon

their march to Bor, but officials said about 5,000 refused to back down.

UN mission facing tough task

The United Nations Mission in the Republic of South Sudan (UNMISS) said the number of those displaced by the conflict had grown to 180,000 people. 75,000 of them have sought refuge in various UNMISS bases around the country. UNMISS's Military Staff Officer Major Kevin Finlay Walls told DW they were facing a tough task of protecting the civilians, especially in Bor. "We've got a considerable amount of people we are mandated to protect and we are doing that to the best of our ability at the moment," the UN peacekeeper said.

"Bor is a strategic location within South Sudan and in this crisis both factions are using it as a point that they want to dominate," Walls added.

The fighting in South Sudan has left, one of the world's biggest aid recipients facing its most significant crisis since it gained independence from its northern neighbor Sudan in 2011.