Sudan's President Omar Hassan al-Bashir announced on Tuesday a two-week unilateral ceasefire in Southern Kordofan state, a week after the U.N. called for an investigation into reports of violence and abuses there.

Tensions have flared in the state -- which borders South Sudan and holds most of the North's known oil reserves -- after South Sudan seceded last month, taking its oilfields with it.

In an unannounced visit to the state capital Kadugli, Bashir also said that foreign organisations would not be allowed into the state and that any aid would be delivered only through the Sudanese Red Crescent organisation.

Many people in Southern Kordofan sided with South Sudan during a 20-year civil war. Tens of thousands have fled since fighting broke out there in June between Sudan's army and fighters, many of them from the region's ethnic Nuba group.

A report by the U.N. human rights office documented alleged violations in Kadugli and the surrounding Nuba mountains including extrajudicial killings, illegal detention, enforced disappearances, attacks against civilians, looting of homes and mass displacement.