As three weeks of peace talks failed to quell the rising violence in South Sudan, the United Nations has warned of mounting atrocities by both sides.

The fighting began on December 15 after South Sudan President Salva Kiir accused his former deputy, Riek Machar of attempting a coup.

“I can announce that in a couple of weeks there will be a comprehensive report on human rights violations that occurred after 15th of December,” said U.N. Assistant Secretary General for Human Rights, Ivan Simonovic, in an interview with the U.N. station Radio Miraya.

In the course of his visit, Mr. Simonovic said he spotted bodies of civilians decomposing on the streets of Bentiu. The victims, he said, had been tied up before they were shot – suggesting a clear violation of the norms of combat.

Recent estimates have suggested that the month-long conflict could already have claimed 10,000 lives with as many as 460,000 people displaced, according to the UN. In an email, a U.N. official said the fighting had intensified in around the towns of Bor, the capital of Jonglei state, and Malakal – a town that both sides claim to control.

The conflict has also drawn in regional powers as Uganda has confirmed that some of its soldiers have been killed while fighting on the side of the Government forces.

“Only the other day, January 13, the SPLA and elements of our army had a big battle with the rebel troops about 90 km from Juba where we inflicted a big defeat on them,” said Ugandan President Yoweri Museveni on Wednesday at a regional conference in Angola, “Unfortunately, many lives were lost on the side of the rebels. We also took casualties and had some dead.”

Uganda has maintained that its soldiers are merely guarding vital installations, yet rebel military spokesperson, General Lul Koang said the Ugandan air force has been bombing rebel positions. “They are providing close air support to government forces,” he said.

In Addis Ababa, delegates from both sides have been unable to hammer out an agreement for the cessation of hostilities despite three weeks of negotiations. The sticking points, officials said, is the release of 11 senior politicians imprisoned by President Kiir, and the complications created by the presence of Ugandan forces on the ground.

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