Two warring factions from South Sudan are holding more advanced peace talks for the first time since conflict began in the country on December 15.

Twenty-five thousand young men who make up a tribal militia known as the “White Army” are marching towards a contested state capital in South Sudan, an official has said, reducing hopes for a ceasefire.

South Sudan’s government has agreed at a meeting of East African leaders to end hostilities against rebels accused of trying to overthrow the young country’s regime, but the ceasefire was quickly thrown into doubt because the head of the rebellion was not invited.