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 to end hostilities, regional African leaders say.

Clashes in Darfur between Arab nomads and south Sudan’s army along the country’s volatile north-south border left dozens dead and more wounded, Sudanese officials said.