NAIROBI: Warring forces on both sides of South Sudan's brutal civil war have likely carried out crimes against humanity, the UN said Thursday, a day ahead of planned peace talks.

 

Warning of "countless" gross violations of human rights, the UN peacekeeping mission in South Sudan said that "there are reasonable grounds to believe that crimes against humanity have been committed during the conflict by both government and opposition forces."

 

The UN's report was released amid preparations for talks slated between President Salva Kiir and rebel chief Riek Machar in the Ethiopian capital to stem almost five months of bloodshed.

 

Presidential spokesman Chaat Paul told AFP that Kiir would fly to Addis Ababa early Friday. An AFP photographer saw Machar arrive in the Ethiopian capital on Thursday evening.

 

"Countless incidents of gross violations of human rights and serious violations of humanitarian law have occurred during the conflict in South Sudan," said the UN report, based on over 900 interviews with victims and witnesses.

 

"These include extrajudicial killings, enforced disappearances, rape, the direct targeting of civilians, often along ethnic lines, as well as ill-treatment and the destruction of property. These are crimes for which perpetrators bear individual criminal responsibility."

 

While both leaders speak of peace, fierce fighting continues and the United Nations has warned of the risk of severe famine and genocide.

 

With a January ceasefire in tatters, the UN report said that "fighting continues with little hope that civilians will see any respite from the relentless violence."

 

Although starting as a personal rivalry between Kiir and Machar, the conflict has seen the army divide along ethnic lines, pitting members of Kiir's Dinka tribe against Machar's Nuer.

 

The United States this week unveiled its first sanctions in response to the "unthinkable violence", targeting one military leader from each side.

 

The war has claimed thousands -- and possibly tens of thousands -- of lives, with over 1.2 million people forced to flee their homes.

 

The report detailed horrific killings, including in the first days after fighting broke out in the capital Juba on December 15.

 

One Nuer man recounted to UN rights workers how army troops raided houses and shot civilians in Juba.

 

"Nuer were being killed like chickens," he was quoted as saying.

 

"Witness after witness recounted horror as they watched security forces enter their communities, sometimes in tanks and with heavy weaponry, and round up their relatives and neighbours," the report added.

 

"In some cases, victims were killed immediately; in others, they were taken to other locations and killed."

 

In other areas, Dinka people were targeted for their ethnicity and killed, including in massacres in the northern oil town of Bentiu, where fighting continues.

 

Aid agencies are warning that South Sudan is now on the brink of Africa's worst famine since the 1980s, while both US Secretary of State John Kerry and UN human rights chiefs have spoken out over their fears that the country could slide towards a genocide.

 

But as pressure builds to stem the brutal conflict, fears are growing that political leaders can no longer hold back their warring forces as communities spiral into cycles of revenge attacks, Amnesty International said in a report Thursday.

 

Testimonies in Amnesty's report describe civilians including children executed by the side of road "like sheep", gang raping of women using sticks, and other victims "grotesquely mutilated" with their lips sliced off.

 

In one case, a woman who was three months pregnant was gang-raped by 14 men and then forced to watch seven women who refused to be raped killed as gunmen forced sticks instead into their vaginas.

 

"The longer ethnic rivalries are allowed to deepen and fester, the more fragmented South Sudan will become, making reconciliation and sustainable peace much more difficult to achieve," Amnesty warned.

 

The conflict erupted on December 15 with Kiir accusing Machar of attempting a coup. Machar then fled to the bush to launch a rebellion, insisting that the president had attempted to carry out a bloody purge of his rivals.