UN approves more South Sudan peacekeepers

The United Nations Security Council has approved plans to almost double the number of UN peacekeepers in South Sudan.

The 15-member council unanimously authorised on Tuesday a request by UN Secretary-General Ban Ki-moon to boost the strength of the UN mission in South Sudan to 12,500 troops and 1,323 police - up from its previous mandate of 7,000 troops and 900 police.

Earlier on Tuesday the top UN humanitarian chief in the country said thousands of South Sudanese have been killed in the week-long violence, giving the first clear indication of the scale of conflict engulfing the young nation.

"Absolutely no doubt in my mind that we're into the thousands" of dead, Toby Lanzer told reporters on Tuesday.

The official death toll has stood at 500 for days, although numbers are feared to be far higher, with some estimating at least a 1,000.

Hilde Johnson, head of the UN peacekeeping mission in South Sudan said that "terrible atrocities have been committed and perpetrators will have to be held accountable."

She said the situation "will turn into a large scale humanitarian crisis if the violence does not stop."

UN rights chief Navi Pillay said on Tuesday that a mass grave had been found in the rebel-held town of Bentiu, while there were "reportedly at least two other mass graves" in the capital Juba.

The grim discoveries follow more than a week of escalating battles between troops loyal to President Salva Kiir and those backing his rival Riek Machar, a former vice president who was sacked in July.

Machar's forces were driven from the town of Bor on Tuesday by the army, but still hold Bentiu, capital of the key oil-producing state of Unity.

Lanzer said the situation in Bentiu remained "tense."

"There are a lot of armed men, almost no civilians on the street," he said to AFP.

"There are now well over 7,000 civilians within the UN base, where they've had to extend the perimeter."

Fighting has spread to half of the nation's 10 states, with hundreds of thousands fleeing to the countryside, prompting warnings of an imminent humanitarian disaster.

Machar said, for the first time, on Tuesday that he was ready to accept Kiir's offer of talks, suggesting neighbouring Ethiopia as a neutral location.

"We are ready for talks," he told Radio France Internationale (RFI), adding that he had spoken earlier in the day to US Secretary of State John Kerry and Ethiopia's Foreign Minster Teos Adhanom.

"We want democratic free and fair elections. We want Salva Kiir to call it a day," Machar said, listing his demands, which follow days of shuttle diplomacy by African nations and calls from Western powers for fighting to stop.

Machar's promise of talks came shortly before the army stormed Bor town, which Information Minister Michael Makwei called a "gift of the government of South Sudan to the people".

Bor's capture, apparently without major resistance by the rebels, relieves some 17,000 besieged civilians who fled into the overstretched UN peacekeeping compound for protection, severely stretching limited food and supplies.