S. Sudan Army Claims Capture of Rebel Base, Key Oil Town

South Sudan government forces said Sunday they had overrun the key rebel base of Nasir and the northern oil hub of Bentiu following a major offensive that was launched despite international peace efforts.

Army spokesman Philip Aguer told Agence France Presse that the advance had forced rebel leader Riek Machar, who has been fighting President Salva Kiir since mid-December, to flee towards the Ethiopian border.

The attack comes just days after South Sudanese President Salva Kiir agreed during a visit by U.S. Secretary of State John Kerry to hold direct talks with Machar on ending the civil war in the world's youngest nation.

"Our forces captured Nasir this morning. After we launched an assault yesterday with heavy bombardments, the town is ours. The rebels including Riek Machar are fleeing towards the Ethiopian border, we are still advancing," Aguer said.

Nasir, situated close to the border with Ethiopia, has been one of the main bases of Machar and his rebel army.

He said government troops had also moved into the northern oil hub of Bentiu, capital of the oil-rich Unity State and a town that has changed hands several times throughout the conflict.

Independent sources contacted in Bentiu confirmed that government soldiers were now inside the town following a morning of fierce fighting with the rebels.

"Government soldiers are now in Bentiu, they appear to be in control," an independent aid worker in the town said.

Bentiu fell into rebel hands last month, and opposition forces were accused by the United Nations of massacring hundreds of civilians in the town. Both sides in the conflict have been accused of war crimes including mass killings, rape, attacks on hospitals and places of worship and recruiting child soldiers.

Kerry had visited South Sudan on Friday and secured agreement from President Kiir to meet with Machar in Addis Ababa in the coming days, with Ethiopian Prime Minister Hailemariam Desalegn acting as mediator.

The top U.S. diplomat, who brandished the threat of sanctions if either Kiir or Machar fail to end their war, said he hoped the two would agree to finally implement a moribund ceasefire deal and set up a transitional government.

President Barack Obama signed a decree last month authorising punitive sanctions, including the seizure of assets and visa bans, against anyone in South Sudan deemed to be threatening peace efforts.

However the independent Sudan Tribune website said it interviewed Machar in a rebel-held part of the country after Kerry's visit, and quoted Machar as saying that face-to-face talks "may be counter-productive."

The war in the world's youngest country has claimed thousands -- and possibly tens of thousands -- of lives, with at least 1.2 million people forced to flee their homes, many living in appalling conditions in overstretched U.N. bases and in fear of ethnic violence.

Aid agencies are also warning that South Sudan is on the brink of Africa's worst famine since the 1980s, while both Kerry and the U.N. human rights chief have spoken out over their fears that the country could slide towards a genocide.

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.